View source for GCHQ

{{Short description|British signals intelligence agency}}
{{Distinguish|HM Government Communications Centre|Conservative Campaign Headquarters}}
{{Use dmy dates|date=July 2022}}
{{Use British English|date=August 2020}}
{{Infobox government agency
| agency_name     = Government Communications Headquarters
| nativename      = 
| nativename_a    = 
| nativename_r    = 
| logo            = GCHQ logo.svg
| logo_width      = 
| logo_caption    = 
| picture         = Aerial of GCHQ, Cheltenham, Gloucestershire, England 24May2017 arp.jpg
| picture_caption = [[The Doughnut]] from above in 2017
| seal            = 
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| formed          = {{start date and age|1919|11|1|df=yes}} (as [[Government Code and Cypher School]])
| preceding1      = [[MI1b]] (Army)
| preceding2      = [[NID25]] (Royal Navy)
| dissolved       = 
| superseding     = 
| jurisdiction    = [[His Majesty's Government]]
| headquarters    = [[The Doughnut]]<br>Hubble Road<br>[[Cheltenham]], England<br>United Kingdom
| coordinates     = {{Coord|51|53|58|N|2|07|28|W|type:landmark_region:GB|display=title,inline}}
| employees       = 7,181<ref name="ISC_2021-2022">{{Cite web |url=https://isc.independent.gov.uk/wp-content/uploads/2022/12/ISC-Annual-Report-2021%E2%80%932022.pdf |title=Intelligence and Security Committee of Parliament "Annual Report 2021–2022" |access-date=20 December 2022 |archive-date=23 December 2022 |archive-url=https://web.archive.org/web/20221223172331/https://isc.independent.gov.uk/wp-content/uploads/2022/12/ISC-Annual-Report-2021%E2%80%932022.pdf |url-status=live }}</ref>
| budget          = [[Single Intelligence Account]] (£3.711 billion in 2021–2022)<ref name="ISC_2021-2022" />
| minister1_name  = [[David Lammy]]
| minister1_pfo   = [[Secretary of State for Foreign and Commonwealth Affairs]]
| minister2_name  = 
| minister2_pfo   = 
| chief1_name     = [[Anne Keast-Butler]]
| chief1_position = [[Director of GCHQ]]
| chief2_name     = 
| chief2_position = 
| child1_agency   = [[National Cyber Security Centre (United Kingdom)|National Cyber Security Centre]]
| child2_agency   = Composite Signals Organisation
| website         = {{Official URL}}
| footnotes       = {{reflist|group="nb"}}
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}}
'''Government Communications Headquarters''' ('''GCHQ''') is an [[intelligence agency|intelligence]] and [[security agency|security]] organisation responsible for providing [[signals intelligence]] (SIGINT) and [[information assurance]] (IA) to the [[Government of the United Kingdom|government]] and [[British Armed Forces|armed forces]] of the [[United Kingdom]].<ref>[http://www.gchq.gov.uk/who_we_are/Pages/Welcome-to-GCHQ.aspx GCHQ – Welcome to GCHQ] {{Webarchive|url=https://web.archive.org/web/20141022234355/http://www.gchq.gov.uk/who_we_are/Pages/Welcome-to-GCHQ.aspx |date=22 October 2014 }}, Government of the United Kingdom. Retrieved 7 July 2014.</ref> Primarily based at [[The Doughnut]] in the suburbs of [[Cheltenham]], GCHQ is the responsibility of the country's [[Secretary of State for Foreign and Commonwealth Affairs]] (Foreign Secretary), but it is not a part of the [[Foreign Office]] and its director ranks as a [[Permanent secretary (UK)|Permanent Secretary]].

GCHQ was originally established after the [[First World War]] as the [[Government Code and Cypher School]] (GC&CS)<ref>Headrick, Daniel R. (1991) ''The invisible Weapon: Telecommunications and International Politics 1851-1945'', Oxford UP p219</ref> and was known under that name until 1946. During the [[Second World War]] it was located at [[Bletchley Park]], where it was responsible for breaking the German [[Enigma machine|Enigma codes]]. There are two main components of GCHQ, the Composite Signals Organisation (CSO), which is responsible for gathering information, and the [[National Cyber Security Centre (United Kingdom)|National Cyber Security Centre]] (NCSC), which is responsible for securing the UK's own communications. The Joint Technical Language Service (JTLS) is a small department and cross-government resource responsible for mainly technical language support and translation and interpreting services across government departments. It is co-located with GCHQ for administrative purposes.

In 2013, GCHQ received considerable media attention when the former [[National Security Agency]] contractor [[Edward Snowden]] revealed that the agency was in the process of collecting all online and telephone data in the UK via the [[Tempora]] programme.<ref>{{cite magazine|url = https://www.wired.co.uk/news/archive/2013-06/24/gchq-tempora-101|title = A simple guide to GCHQ's internet surveillance programme Tempora|magazine = Wired UK|date = 24 June 2013|access-date = 29 August 2017|archive-date = 15 May 2016|archive-url = https://web.archive.org/web/20160515020741/http://www.wired.co.uk/news/archive/2013-06/24/gchq-tempora-101|url-status = live}}</ref> Snowden's revelations began a spate of ongoing [[Global surveillance disclosures (2013–present)|disclosures of global surveillance]]. ''[[The Guardian]]'' newspaper was forced to destroy computer hard drives with the files Snowden had given them because of the threats of a lawsuit under the Official Secrets Act.<ref>{{cite news|url=https://www.theguardian.com/world/2013/aug/20/nsa-snowden-files-drives-destroyed-london|title=NSA files: why the Guardian in London destroyed hard drives of leaked files|work=The Guardian|first=Julian|last=Borger|date=21 August 2013|access-date=27 May 2018|archive-date=4 February 2017|archive-url=https://web.archive.org/web/20170204030346/https://www.theguardian.com/world/2013/aug/20/nsa-snowden-files-drives-destroyed-london|url-status=live}}</ref> In June 2014, ''[[The Register]]'' reported that the information the government sought to suppress by destroying the hard drives related to the location of a "beyond top secret" GCHQ internet monitoring base in [[Seeb]], Oman, and the close involvement of [[BT Group|BT]] and [[Cable & Wireless plc|Cable & Wireless]] in intercepting internet communications.<ref>{{cite web |url=https://www.theregister.co.uk/2014/06/03/revealed_beyond_top_secret_british_intelligence_middleeast_internet_spy_base |title=Revealed: GCHQ's beyond top secret middle eastern internet spy base |work=The Register |first=Duncan |last=Campbell |author-link=Duncan Campbell (journalist, born 1952) |date=3 June 2014 |access-date=16 September 2017 |archive-date=25 June 2014 |archive-url=https://web.archive.org/web/20140625063147/http://www.theregister.co.uk/2014/06/03/revealed_beyond_top_secret_british_intelligence_middleeast_internet_spy_base/ |url-status=live }}</ref>

==Structure==
GCHQ is led by the Director of GCHQ, [[Anne Keast-Butler]], and a Corporate Board, made up of executive and non-executive directors. Reporting to the Corporate Board are:{{sfn|Aldrich|2010|p=565}}<ref name="Leong">(secondary) {{cite book |url=https://books.google.com/books?id=bnEk6zmoR0MC&pg=PA87 |first=Angela |last=Leong |title=The Disruption of International Organised Crime: An Analysis of Legal and Non-Legal Strategies |year=2007 |publisher=Ashgate Publishing |access-date=19 April 2012|isbn=978-0-7546-7066-7 }}</ref>
*Sigint missions: comprising maths and [[cryptanalysis]], IT and computer systems, linguistics and translation, and the intelligence analysis unit
*Enterprise: comprising applied research and emerging technologies, corporate knowledge and information systems, commercial supplier relationships, and [[biometrics]]
*Corporate management: enterprise resource planning, [[human resources]], internal audit, and architecture
*National Cyber Security Centre (NCSC).<ref name="ferris">Ferris (2020)</ref>

==History==
{{See also|Ultra (cryptography)|l1=Second World War activities of GC&CS referred to as 'Ultra'}}

===World War I===
During the First World War, the [[British Army]] and [[Royal Navy]] had separate signals intelligence agencies, [[MI1b]] and [[NID25]] (initially known as Room 40) respectively.<ref>{{cite book |first=Paul |last=Gannon |title=Inside Room 40: The Codebreakers of World War I |publisher=Ian Allan Publishing |year=2011 |isbn=978-0-7110-3408-2}}</ref><ref>Johnson, 1997, p. 27</ref> 

===Interwar Period===
{{anchor|Government Code and Cypher School}}
In 1919, the Cabinet's Secret Service Committee, chaired by [[Lord Curzon]], recommended that a peacetime codebreaking agency should be created, a task which was given to the [[Naval Intelligence Division (UK)|Director of Naval Intelligence]], [[Hugh Sinclair]].<ref name="johnson44">Johnson, 1997, p. 44</ref> Sinclair merged staff from NID25 and MI1b into the new organisation, which initially consisted of around 25–30 officers and a similar number of clerical staff.<ref>Johnson, 1997, p. 45 and Kahn, 1991, p. 82; these sources give different numbers for the initial size of the GC&CS staff</ref> It was titled the "Government Code and Cypher School" (GC&CS), a cover-name which was chosen by Victor Forbes of the [[Foreign Office]].<ref>{{Cite book|last=Macksey|first=Kenneth|title=The Searchers: How Radio Interception Changed the Course of Both World Wars|year=2003| publisher=Cassell Military|isbn=0-304-36545-9|page=58}}</ref> [[Alastair Denniston]], who had been a member of NID25, was appointed as its operational head.<ref name="johnson44"/> It was initially under the control of the [[British Admiralty|Admiralty]] and located in Watergate House, Adelphi, London.<ref name="johnson44"/> Its public function was "to advise as to the security of codes and cyphers used by all Government departments and to assist in their provision", but also had a secret directive to "study the methods of cypher communications used by foreign powers".<ref>Smith, 2001, pp. 16–17</ref> GC&CS officially formed on 1 November 1919,<ref>Kahn, 1991, p. 82</ref> and produced its first decrypt prior to that date, on 19 October.<ref name="johnson44"/>

[[File:Allidina-Visram.jpg|thumbnail|right|Allidina Visram school in Mombasa, pictured above in 2006, was the location of the British "Kilindini" codebreaking outpost during World War II.]]

Before the Second World War, GC&CS was a relatively small department. By 1922, the main focus of GC&CS was on diplomatic traffic, with "no service traffic ever worth circulating"<ref name="and">{{cite journal |first=Alastair G. |last=Denniston |title=The Government Code and Cypher School Between the Wars |journal=Intelligence and National Security |volume=1 |issue=1 |pages=48–70 |year=1986 |doi=10.1080/02684528608431841 }}</ref> and so, at the initiative of Lord Curzon, it was transferred from the Admiralty to the [[Foreign Office]].<ref>Smith, 2001, pp. 20–21</ref> GC&CS came under the supervision of [[Hugh Sinclair]], who by 1923 was both the Chief of [[Secret Intelligence Service|SIS]] and Director of GC&CS.<ref name="johnson44"/> In 1925, both organisations were co-located on different floors of Broadway Buildings, opposite [[St. James's Park]].<ref name="johnson44"/> Messages decrypted by GC&CS were distributed in blue-jacketed files that became known as "BJs".<ref>Smith, 2001, pp. 18–19</ref> In the 1920s, GC&CS was successfully reading Soviet Union diplomatic cyphers. However, in May 1927, during a row over clandestine Soviet support for the [[1926 United Kingdom general strike|General Strike]] and the distribution of subversive propaganda, Prime Minister [[Stanley Baldwin]] made details from the decrypts public.{{sfn|Aldrich|2010|p= 18}}

===World War II===
During the Second World War, GC&CS was based largely at [[Bletchley Park]], in present-day [[Milton Keynes]], working on understanding the German [[Enigma machine]] and [[Lorenz cipher]]s.<ref>{{cite book |first=Paul |last=Gannon |title=Colossus: Bletchley Park's Greatest Secret |publisher=Atlantic Books |year=2006 |isbn=978-1-84354-331-2}}</ref> In 1940, GC&CS was working on the diplomatic codes and ciphers of 26 countries, tackling over 150 diplomatic cryptosystems.<ref>{{cite book |first=David |last=Alvarez |chapter=Most Helpful and Cooperative: GC&CS and the Development of American Diplomatic Cryptanalysis, 1941–1942 |title=Action This Day: Bletchley Park from the Breaking of the Enigma Code to the Birth of the Modern Computer |editor1-first=Michael |editor1-last=Smith |editor2-first=Ralph| editor2-last=Erskine |publisher=Bantam Press |year=2001 |isbn=978-0593049105}}</ref> Senior staff included [[Alastair Denniston]], [[Oliver Strachey]], [[Dilly Knox]], [[John Tiltman]], [[Edward Travis]], [[Ernst Fetterlein]], [[Josh Cooper (cryptographer)|Josh Cooper]], [[Donald Michie]], [[Alan Turing]], [[Gordon Welchman]], [[Joan Clarke]], [[Max Newman]], [[William Tutte]], [[I. J. Good|I. J. (Jack) Good]], [[Peter Calvocoressi]] and [[Hugh Foss]].<ref>{{Citation | editor-last = Erskine | editor-first = Ralph | editor2-last = Smith | editor2-first = Michael | editor2-link = Michael Smith (newspaper reporter) | title = The Bletchley Park Codebreakers | publisher = Biteback Publishing Ltd | year = 2011 | isbn = 978-1-84954-078-0}}</ref> The 1943 British–US Communication Intelligence Agreement, [[1943 BRUSA Agreement|BRUSA]], connected the signal intercept networks of the GC&CS and the US [[National Security Agency]] (NSA).<ref>{{Cite news |date=2016-02-08 |title=How the British and Americans started listening in |language=en-GB |work=BBC News |url=https://www.bbc.com/news/magazine-35491822 |access-date=2023-04-02 |archive-date=2 April 2023 |archive-url=https://web.archive.org/web/20230402082849/https://www.bbc.com/news/magazine-35491822 |url-status=live }}</ref><ref>{{Cite news |date=2021-03-05 |title=Diary reveals birth of secret UK-US spy pact that grew into Five Eyes |language=en-GB |work=BBC News |url=https://www.bbc.com/news/uk-56284453 |access-date=2023-04-02 |archive-date=2 April 2023 |archive-url=https://web.archive.org/web/20230402082850/https://www.bbc.com/news/uk-56284453 |url-status=live }}</ref> Equipment used to break enemy codes included the [[Colossus computer]].<ref>{{Citation |editor-last= Preneel |editor-first= Bart |title= Advances in Cryptology - EUROCRYPT 2000: International Conference on the Theory and Application of Cryptographic Techniques Bruges, Belgium May 14-18, 2000, Proceedings |publisher=  Springer |series= Lecture Notes in Computer Science |year= 2000 |volume= 1807 |isbn= 978-3540675174|contribution-url=https://www.iacr.org/archive/eurocrypt2000/1807/18070423-new.pdf |archive-url=https://web.archive.org/web/20081120221724/http://www.iacr.org/archive/eurocrypt2000/1807/18070423-new.pdf |archive-date=2008-11-20 |url-status=live |contribution=Colossus and the German Lorenz Cipher – Code Breaking in WW II |page=417 |doi=10.1007/3-540-45539-6_29 |doi-access= free }}</ref> Colossus consisted of ten networked computers.<ref>{{cite news|url=https://www.bbc.com/news/technology-67997406 |title=Unseen images of code breaking computer that helped win WW2|date= 17 January 2024|first= Shiona|last= McCallum|newspaper=BBC|access-date=21 January 2024}}</ref>

An outstation in the Far East, the [[Far East Combined Bureau]], was set up in Hong Kong in 1935 and moved to Singapore in 1939. Subsequently, with the Japanese advance down the Malay Peninsula, the Army and RAF codebreakers went to the [[Wireless Experimental Centre]] in Delhi, India. The Navy codebreakers in FECB went to [[Colombo]], Ceylon, then to [[Kilindini]], near [[Mombasa]], Kenya.<ref>{{cite web|url=http://www.coastweek.com/codes.htm|title=Mombasa was base for high-level UK espionage operation|publisher=Coastweek|access-date=25 February 2018|archive-date=15 May 2013|archive-url=https://web.archive.org/web/20130515123737/http://www.coastweek.com/codes.htm|url-status=usurped}}</ref>

===Post Second World War===
GC&CS was renamed the Government Communications Headquarters (GCHQ) in June 1946.<ref>{{Cite book|last= Smith|first=Michael|title=Station X|year=1998|publisher=Channel 4 books|isbn=0-330-41929-3|page= 176}}</ref>

The organisation was at first based in [[RAF Eastcote|Eastcote]] in northwest London, then in 1951<ref>{{cite web|url=http://www.gchq.gov.uk/about/moving5.html|title=History of GCHQ Cheltenham|work=GCHQ website 'About Us' pages|access-date=29 June 2006 |archive-url = https://web.archive.org/web/20061005175413/http://www.gchq.gov.uk/about/moving5.html <!-- Bot retrieved archive --> |archive-date = 5 October 2006}}</ref> moved to the outskirts of [[Cheltenham]], setting up two sites at [[Oakley, Gloucestershire|Oakley]] and [[Benhall, Cheltenham|Benhall]]. One of the major reasons for selecting Cheltenham was that the town had been the location of the headquarters of the [[United States Army Services of Supply]] for the European Theater during the War, which built up a telecommunications infrastructure in the region to carry out its logistics tasks.<ref>{{cite web |url=https://www.theregister.com/2013/05/24/geeks_guide_gchq/?page=1 |title=INSIDE GCHQ: Welcome to Cheltenham's cottage industry |last=Dormon |first=Bob |date=24 May 2013 |website=[[The Register]] |access-date=6 September 2016 |archive-date=6 September 2021 |archive-url=https://web.archive.org/web/20210906130613/https://www.theregister.com/2013/05/24/geeks_guide_gchq/?page=1 |url-status=live }}</ref>

Following the [[Second World War]], US and British intelligence have shared information as part of the [[UKUSA Agreement]]. The principal aspect of this is that GCHQ and its US equivalent, the National Security Agency (NSA), share technologies, infrastructure and information.<ref>{{cite book |title=Dirty Diplomacy |first=Craig |last=Murray |date=16 October 2007 |publisher=Scribner |page=332 |isbn=978-1416548010}}</ref><ref name="ferris"/>

GCHQ ran many [[signals intelligence]] (SIGINT) monitoring stations abroad. During the early [[Cold War]], the remnants of the [[British Empire]] provided a global network of ground stations which were a major contribution to the UKUSA Agreement; the US regarded [[RAF Little Sai Wan]] in [[Hong Kong]] as the most valuable of these. The monitoring stations were largely run by inexpensive [[Conscription in Great Britain#After 1945|National Service]] recruits, but when this ended in the early 1960s, the increased cost of civilian employees caused budgetary problems. In 1965 a Foreign Office review found that 11,500 staff were involved in SIGINT collection (8,000 GCHQ staff and 3,500 military personnel), exceeding the size of the [[Her Majesty's Diplomatic Service|Diplomatic Service]]. Reaction to the [[Suez War]] led to the eviction of GCHQ from several of its best foreign SIGINT collection sites, including the new [[Far East Combined Bureau|Perkar, Ceylon site]] and [[RAF Habbaniya]], Iraq. The staff largely moved to tented encampments on military bases in Cyprus, which later became the [[Sovereign Base Area]].<ref name="aldrich-2011" >{{cite book |pages=117–118, 153, 155, 160–162, 227–228, 475 |url=https://books.google.com/books?id=l9i5bt1-7HYC |last=Aldrich |first=Richard J. |year=2011 |title=GCHQ |location=London |publisher=Harper Press |isbn=978-0-007312-665 |access-date=21 March 2023 |archive-date=4 April 2023 |archive-url=https://web.archive.org/web/20230404131620/https://books.google.com/books?id=l9i5bt1-7HYC |url-status=live }}</ref>

During the [[Cuban Missile Crisis]], [[GCHQ Scarborough]] intercepted radio communications from Soviet ships reporting their positions and used that to establish where they were heading. A copy of the report was sent directly to the White House Situation Room, providing initial indications of Soviet intentions with regards the US naval blockade of Cuba.<ref name=":0">{{Cite news |last=Corera |first=Gordon |date=2019-10-21 |title=Scarborough's Cuban missile crisis role revealed |language=en-GB |url=https://www.bbc.com/news/uk-50098955 |access-date=2019-10-21 |archive-date=5 December 2019 |archive-url=https://web.archive.org/web/20191205204023/https://www.bbc.com/news/uk-50098955 |url-status=live }}</ref>

[[Duncan Campbell (journalist, born 1952)|Duncan Campbell]] and [[Mark Hosenball]] revealed the existence of GCHQ in 1976 in an article for ''[[Time Out (magazine)|Time Out]]''; as a result, Hosenball was deported from the UK.<ref>{{cite magazine |magazine=Time Out |title=The Eavesdroppers |author1=Duncan Campbell |author2=Mark Hosenball |url=http://www.duncancampbell.org/PDF/1976-may-time-out-the-eavesdroppers.pdf |archive-url=https://web.archive.org/web/20131101152620/http://www.duncancampbell.org/PDF/1976-may-time-out-the-eavesdroppers.pdf |archive-date=2013-11-01 |url-status=live |date=21 May 1976 |access-date=1 March 2016}}</ref><ref>Court ruling, "[http://www.uniset.ca/other/css/hosenball.html R v Secretary of State for the Home Department, ex parte Hosenball] {{Webarchive|url=https://web.archive.org/web/20160521131820/http://www.uniset.ca/other/css/hosenball.html |date=21 May 2016 }}", [1977] 1 W.L.R. 766; [1977] 3 All E.R. 452.  Lord Denning presiding judge, 29 March 1977.</ref> GCHQ had a very low profile in the media until 1983 when the trial of [[Geoffrey Prime]], a [[KGB]] mole within it, created considerable media interest.{{sfn|Aldrich|2010|p= 382}}

====Trade union disputes====
{{Main|Council of Civil Service Unions v Minister for the Civil Service|GCHQ trade union ban}}
[[File:NUCPS banner.jpg|thumb|right|[[NUCPS]] banner on march in [[Cheltenham]] 1992]]
In 1984, GCHQ was the centre of a political row when, in the wake of strikes which affected Sigint collection, the [[Conservative Party (UK)|Conservative]] government of [[Margaret Thatcher]] prohibited its employees from belonging to a trade union, asserting that membership of a union was in conflict with [[national security]].<ref name="ferris"/> The government offered £1,000 to each employee who agreed to give up their right to union membership. Following the breakdown of talks and the failure to negotiate a no-strike agreement, a number of mass national one-day strikes were held to protest against this decision, believed by some to be the first step to wider bans on trade unions. Appeals to British courts and the [[European Commission of Human Rights]]<ref>{{cite web |url=http://cmiskp.echr.coe.int/tkp197/view.asp?action=html&documentId=664551&portal=hbkm&source=externalbydocnumber&table=F69A27FD8FB86142BF01C1166DEA398649 |title=EComHR Inadmissibility decision of EComHR on application no. 11603/85 |year=1987 |access-date=15 November 2010 |archive-date=4 June 2012 |archive-url=https://web.archive.org/web/20120604022433/http://cmiskp.echr.coe.int/tkp197/view.asp?action=html&documentId=664551&portal=hbkm&source=externalbydocnumber&table=F69A27FD8FB86142BF01C1166DEA398649 |url-status=live }}</ref> were unsuccessful. An appeal to the [[International Labour Organization]] resulted in a decision that the government's actions were in violation of [[Freedom of Association and Protection of the Right to Organise Convention]].<ref>{{cite web |url=http://cmiskp.echr.coe.int/tkp197/view.asp?action=html&documentId=664551&portal=hbkm&source=externalbydocnumber&table=F69A27FD8FB86142BF01C1166DEA398649 |title=EComHR Inadmissibility decision of EComHR on application no. 11603/85 – The Facts |access-date=15 November 2010 |archive-date=4 June 2012 |archive-url=https://web.archive.org/web/20120604022433/http://cmiskp.echr.coe.int/tkp197/view.asp?action=html&documentId=664551&portal=hbkm&source=externalbydocnumber&table=F69A27FD8FB86142BF01C1166DEA398649 |url-status=live }} para. IV</ref>

A no-strike agreement was eventually negotiated and the ban lifted by the incoming [[Labour Party (UK)|Labour]] government in 1997, with the Government Communications Group of the [[Public and Commercial Services Union]] (PCS) being formed to represent interested employees at all grades.<ref>{{cite web|url=http://www.gchq.gov.uk/recruitment/union.html |title=Union representation |work=GCHQ website |access-date=12 April 2006 |url-status=dead |archive-url=https://web.archive.org/web/20060509054114/http://www.gchq.gov.uk/recruitment/union.html |archive-date=9 May 2006 }}</ref><ref name="ferris"/> In 2000, a group of 14 former GCHQ employees, who had been dismissed after refusing to give up their union membership, were offered re-employment, which three of them accepted.<ref>{{cite news|url=http://news.bbc.co.uk/1/hi/uk/627574.stm|title=Sacked GCHQ workers win compensation|work=BBC News|date=1 February 2000|access-date=12 April 2006|archive-date=1 September 2017|archive-url=https://web.archive.org/web/20170901074152/http://news.bbc.co.uk/1/hi/uk/627574.stm|url-status=live}}</ref>

The legal case ''[[Council of Civil Service Unions v Minister for the Civil Service]]'' is significant beyond the dispute, and even beyond trade union law, in that it held for the first time that the [[royal prerogative]] is generally subject to [[judicial review]], although the House of Lords ruled in favour of the Crown in this instance.<ref>{{cite book |first=Ewan |last=McGaughey |title=A Casebook on Labour Law |chapter-url={{GBurl|Wnx7DwAAQBAJ|page=323}} |publisher=Hart |date=2019 |chapter=8: Trade Unions |isbn=978-1-84946-931-9|page=360}}</ref>

===Post Cold War===

====1990s: Post-Cold War restructuring====
The [[Intelligence Services Act 1994]] formalised the activities of the intelligence agencies for the first time, defining their purpose, and the British Parliament's [[Intelligence and Security Committee]] was given a remit to examine the expenditure, administration and policy of the three intelligence agencies.<ref name="ISC">{{cite web|title=ISC – About|url=http://isc.independent.gov.uk/|publisher=Intelligence and Security Committee of Parliament|access-date=1 December 2013|archive-date=25 December 2010|archive-url=https://web.archive.org/web/20101225070246/http://isc.independent.gov.uk/|url-status=live}}</ref> The objectives of GCHQ were defined as working as "in the interests of national security, with particular reference to the defence and foreign policies of His Majesty's government; in the interests of the economic wellbeing of the United Kingdom; and in support of the prevention and the detection of serious crime".<ref name="InTel94">{{cite web|title=Intelligence Services Act 1994|url=http://www.legislation.gov.uk/ukpga/1994/13/section/3|publisher=The National Archives|access-date=1 December 2013|archive-date=2 December 2013|archive-url=https://web.archive.org/web/20131202105208/http://www.legislation.gov.uk/ukpga/1994/13/section/3|url-status=live}}</ref> During the introduction of the Intelligence Agency Act in late 1993, the former Prime Minister [[Jim Callaghan]] had described GCHQ as a "full-blown bureaucracy", adding that future bodies created to provide oversight of the intelligence agencies should "investigate whether all the functions that GCHQ carries out today are still necessary."<ref name="Dec93Hans">{{cite web|title=Hansard: December 1993 Intelligence Services Bill|work=[[Hansard|Parliamentary Debates (Hansard)]]|date=9 December 1993|url=https://api.parliament.uk/historic-hansard/lords/1993/dec/09/intelligence-services-bill-hl|access-date=11 March 2014|archive-date=19 March 2014|archive-url=https://web.archive.org/web/20140319035248/http://hansard.millbanksystems.com/lords/1993/dec/09/intelligence-services-bill-hl|url-status=live}}</ref>

In late 1993 civil servant [[Michael Quinlan (civil servant)|Michael Quinlan]] advised a deep review of the work of GCHQ following the conclusion of his "Review of Intelligence Requirements and Resources", which had imposed a 3% cut on the agency.{{sfn|Aldrich|2010|p=493}} The [[Chief Secretary to the Treasury]], [[Jonathan Aitken]], subsequently held face to face discussions with the intelligence agency directors to assess further savings in the wake of Quinlan's review. Aldrich (2010) suggests that Sir [[John Adye]], the then Director of GCHQ performed badly in meetings with Aitken, leading Aitken to conclude that GCHQ was "suffering from out-of-date methods of management and out-of-date methods for assessing priorities".{{sfn|Aldrich|2010|p=494}} GCHQ's budget was £850&nbsp;million in 1993, (£{{Formatprice|{{Inflation|UK|850000000|1993|{{inflation-year|UK}}|r=0}}}} as of {{inflation-year|UK}}){{Inflation-fn|UK}} compared to £125&nbsp;million for the Security Service and SIS (MI5 and MI6). In December 1994 the businessman Roger Hurn was commissioned to begin a review of GCHQ, which was concluded in March 1995.<ref name="Aldrich, 2010, 495" >{{harvnb|Aldrich|2010|p=495}}</ref> Hurn's report recommended a cut of £100&nbsp; million in GCHQ's budget; such a large reduction had not been suffered by any British intelligence agency since the end of World War II.<ref name="Aldrich, 2010, 495"/> The J Division of GCHQ, which had collected SIGINT on Russia, disappeared as a result of the cuts.<ref name="Aldrich, 2010, 495"/> The cuts had been mostly reversed by 2000 in the wake of threats from [[violent non-state actor]]s, and risks from increased terrorism, organised crime and illegal access to nuclear, chemical and biological weapons.<ref name="Aldrich, 2010, 505" >{{harvnb|Aldrich|2010|p=505}}</ref>

[[David Omand]] became the Director of GCHQ in 1996, and greatly restructured the agency in the face of new and changing targets and rapid technological change.<ref name="Aldrich, 2010, 496" >{{harvnb|Aldrich|2010|p=496}}</ref> Omand introduced the concept of "Sinews" (or "SIGINT New Systems") which allowed more flexible working methods, avoiding overlaps in work by creating fourteen domains, each with a well-defined working scope.<ref name="Aldrich, 2010, 496"/> The tenure of Omand also saw the construction of a modern new headquarters, intended to consolidate the two old sites at Oakley and Benhall into a single, more open-plan work environment.<ref name="Aldrich, 2010, 496"/> Located on a 176-acre site in Benhall, it would be the largest building constructed for secret intelligence operations outside the United States.{{sfn|Aldrich|2010|p=9}}<ref name="ferris"/>

Operations at GCHQ's [[Chung Hom Kok]] listening station in Hong Kong ended in 1994.<ref name="Aldrich, 2010, 475" >{{harvnb|Aldrich|2010|p=475}}</ref> GCHQ's Hong Kong operations were extremely important to their relationship with the NSA, who contributed investment and equipment to the station. In anticipation of the [[Transfer of sovereignty over Hong Kong|transfer of Hong Kong to the Chinese government]] in 1997, the Hong Kong stations operations were moved to [[Australian Defence Satellite Communications Station]] in [[Geraldton]] in [[Western Australia]].<ref name="West2012">{{cite book|author=Nigel West|title=Historical Dictionary of Signals Intelligence|url=https://books.google.com/books?id=maJbZGwK4BAC&pg=PR27 |date=31 August 2012|publisher=Scarecrow Press|isbn=978-0-8108-7391-9|pages=27–}}</ref>

Operations that used GCHQ's intelligence-gathering capabilities in the 1990s included the monitoring of communications of Iraqi soldiers in the [[Gulf War]], of [[dissident republican]] terrorists and the [[Real IRA]], of the various factions involved in the [[Yugoslav Wars]], and of the criminal [[Kenneth Noye]].<ref name="Aldrich, 2010, 505"/><ref name="West2012"/><ref name="Aldrich, 2010, 473" >{{harvnb|Aldrich|2010|p=473}}</ref> In the mid-1990s GCHQ began to assist in the investigation of [[cybercrime]].<ref name="Aldrich, 2010, 489" >{{harvnb|Aldrich|2010|p=489}}</ref>

====2000s: Coping with the Internet====
{{See also|Global surveillance|Global surveillance disclosures (2013–present)}}
At the end of 2003, GCHQ moved in to its new building. Built on a circular plan around a large central courtyard, it quickly became known as [[the Doughnut]]. At the time, it was one of the largest public-sector building projects in Europe, with an estimated cost of £337 million. The new building, which was designed by [[Gensler]] and constructed by [[Carillion]], became the base for all of GCHQ's [[Cheltenham]] operations.<ref>{{cite news |url=http://news.bbc.co.uk/1/hi/business/931773.stm |title=Carillion set for growth |work=BBC News |date=19 September 2000 |access-date=22 December 2007 |archive-date=27 February 2009 |archive-url=https://web.archive.org/web/20090227151049/http://news.bbc.co.uk/1/hi/business/931773.stm |url-status=live }}</ref>

The public spotlight fell on GCHQ in late 2003 and early 2004 following the sacking of [[Katharine Gun]] after she leaked to ''[[The Observer]]'' a confidential email from agents at the United States' [[National Security Agency]] addressed to GCHQ officers about the wiretapping of UN delegates in the run-up to the [[2003 Iraq war]].<ref>Aldrich, 2010, p. 521</ref>

GCHQ gains its intelligence by monitoring a wide variety of communications and other electronic signals. For this, a number of stations have been established in the UK and overseas. The listening stations are at Cheltenham itself, [[GCHQ Bude|Bude]], [[GCHQ Scarborough|Scarborough]], [[Ascension Island]], and with the United States at [[RAF Menwith Hill]].<ref>{{cite journal |last=Campbell |first=Duncan |author-link=Duncan Campbell (journalist, born 1952) |title=Phone tappers and the state |journal=New Statesman |year=1981 |page=54}}</ref> [[Ayios Nikolaos Station]] in Cyprus is run by the [[British Army]] for GCHQ.<ref>Aldrich, 2010, p. 471</ref>

In March 2010, GCHQ was criticised by the [[Intelligence and Security Committee]] for problems with its IT security practices and failing to meet its targets for work targeted against cyber attacks.<ref>{{cite web |url= http://www.computerworlduk.com/management/government-law/public-sector/news/index.cfm?newsid=19344 |title= 'Cavalier' GCHQ online spy centre loses 35 laptops |publisher= [[Computerworld UK]] |date= 12 March 2010 |access-date= 12 March 2010 |archive-date= 29 July 2012 |archive-url= https://archive.today/20120729004038/http://www.computerworlduk.com/management/government-law/public-sector/news/index.cfm?newsid=19344 |url-status= live }}</ref>

As revealed by [[Edward Snowden]] in ''[[The Guardian]]'', GCHQ spied on foreign politicians visiting the [[2009 G-20 London Summit]] by eavesdropping phonecalls and emails and monitoring their computers, and in some cases even ongoing after the summit via [[keystroke logging]] that had been undertaken during the summit.<ref>''The Guardian'': [https://www.theguardian.com/uk/2013/jun/16/gchq-intercepted-communications-g20-summits GCHQ intercepted foreign politicians' communications at G20 summits] {{Webarchive|url=https://web.archive.org/web/20131018004108/http://www.theguardian.com/uk/2013/jun/16/gchq-intercepted-communications-g20-summits |date=18 October 2013 }}, 16 June 2013</ref>

According to Edward Snowden, at that time GCHQ had two principal umbrella programs for collecting communications:
* "[[Mastering the Internet]]" (MTI) for Internet traffic, which is extracted from fibre-optic cables and can be searched by using the [[Tempora]] computer system.
* "[[Global Telecoms Exploitation]]" (GTE) for telephone traffic.<ref name=bump>{{cite web |url=http://www.theatlanticwire.com/national/2013/06/uk-tempora-program/66490/ |author=Philip Bump |title=The UK Tempora Program Captures Vast Amounts of Data – and Shares with NSA |publisher=The Atlantic Wire |date=21 June 2013 |access-date=23 June 2013 |archive-date=5 November 2013 |archive-url=https://web.archive.org/web/20131105105045/http://www.theatlanticwire.com/national/2013/06/uk-tempora-program/66490/ |url-status=dead }}</ref>

GCHQ has also had access to the US internet monitoring programme [[PRISM]] from at least as far back as June 2010.<ref>{{cite web|title=Statement on GCHQ's Alleged Interception of Communications under the US PRISM Programme|url=https://isc.independent.gov.uk/wp-content/uploads/2021/01/20130717_ISC_statement_GCHQ.pdf|url-status=live|publisher=Intelligence and Security Committee of Parliament|access-date=19 April 2023|date=17 July 2013|archive-date=19 April 2023|archive-url=https://web.archive.org/web/20230419142038/https://isc.independent.gov.uk/wp-content/uploads/2021/01/20130717_ISC_statement_GCHQ.pdf}}</ref> PRISM is said to give the [[National Security Agency]] and FBI easy access to the systems of nine of the world's top internet companies, including Google, Facebook, Microsoft, Apple, Yahoo, and Skype.<ref>{{cite web |url= https://www.bbc.co.uk/news/world-22860964 |title= Scale and significance of NSA snooping claims |publisher= BBC |date= 11 June 2013 |access-date= 20 June 2018 |archive-date= 17 June 2015 |archive-url= https://web.archive.org/web/20150617020056/http://www.bbc.co.uk/news/world-22860964 |url-status= live }}</ref>

From 2013, GCHQ realised that public attitudes to Sigint had changed and its former unquestioned secrecy was no longer appropriate or acceptable. The growing use of the Internet, together with its inherent insecurities, meant that the communications traffic of private citizens were becoming inextricably mixed with those of their targets and openness in the handling of this issue was becoming essential to their credibility as an organisation. The Internet had become a "cyber commons", with its dominance creating a "second age of Sigint". GCHQ transformed itself accordingly, including greatly expanded Public Relations and Legal departments, and adopting public education in cyber security as an important part of its remit.<ref>Ferris (2020), Chapters 14 and 15.</ref>

==== 2010s: Disinformation, discord and division ====
In February 2014, ''The Guardian'', based on documents provided by Snowden, revealed that GCHQ had indiscriminately collected 1.8&nbsp;million private Yahoo webcam images from users across the world.<ref>{{cite news|url=https://www.theguardian.com/world/2014/feb/27/gchq-nsa-webcam-images-internet-yahoo|title=Optic Nerve: millions of Yahoo webcam images intercepted by GCHQ|date=28 February 2014|access-date=2 March 2014|newspaper=The Guardian|last1=Ackerman|first1=Spencer|last2=Ball|first2=James|archive-date=23 September 2016|archive-url=https://web.archive.org/web/20160923234026/https://www.theguardian.com/world/2014/feb/27/gchq-nsa-webcam-images-internet-yahoo|url-status=live}}</ref> In the same month NBC and [[The Intercept]], based on documents released by Snowden, revealed the [[Joint Threat Research Intelligence Group]] and the Computer Network Exploitation units within GCHQ. Their mission was cyber operations based on "dirty tricks" to shut down enemy communications, discredit, and plant misinformation on enemies.<ref name=NBCFeb14>{{cite web|title=Snowden Docs: British Spies Used Sex and 'Dirty Tricks'|url=https://www.nbcnews.com/news/investigations/snowden-docs-british-spies-used-sex-dirty-tricks-n23091|work=[[NBC News]]|access-date=7 February 2014|date=7 February 2014|archive-date=7 February 2021|archive-url=https://web.archive.org/web/20210207161642/https://www.nbcnews.com/news/investigations/snowden-docs-british-spies-used-sex-dirty-tricks-n23091|url-status=live}}</ref> These operations were 5% of all GCHQ operations according to a conference slideshow presented by the GCHQ.<ref name="nbcslideshow22">{{cite web|title=The Snowden Files: British Spies Used Sex and 'Dirty' Tricks|url=http://msnbcmedia.msn.com/i/msnbc/sections/news/snowden_cyber_offensive2_nbc_document.pdf|website=NBC News Investigations|publisher=NBC|access-date=5 April 2015|archive-url=https://web.archive.org/web/20150112222153/http://msnbcmedia.msn.com/i/msnbc/sections/news/snowden_cyber_offensive2_nbc_document.pdf|archive-date=12 January 2015|url-status=dead}}</ref>

Soon after becoming Director of GCHQ in 2014, [[Robert Hannigan]] wrote an article in the ''[[Financial Times]]'' on the topic of [[internet surveillance]], stating that "however much [large US technology companies] may dislike it, they have become the command and control networks of choice for terrorists and criminals" and that GCHQ and its sister agencies "cannot tackle these challenges at scale without greater support from the private sector", arguing that most internet users "would be comfortable with a better and more sustainable relationship between the [intelligence] agencies and the tech companies". Since the [[2013 global surveillance disclosures]], large US technology companies have improved security and become less co-operative with foreign intelligence agencies, including those of the UK, generally requiring a US court order before disclosing data.<ref name="ft-20141103rh">{{cite news |url=http://www.ft.com/cms/s/2/c89b6c58-6342-11e4-8a63-00144feabdc0.html |archive-url=https://ghostarchive.org/archive/20221210/http://www.ft.com/cms/s/2/c89b6c58-6342-11e4-8a63-00144feabdc0.html |archive-date=10 December 2022 |url-access=subscription |title=The web is a terrorist's command-and-control network of choice |author=Robert Hannigan |newspaper=Financial Times |date=3 November 2014 |access-date=3 November 2014}}</ref><ref name="ft-20141103">{{cite news |url=http://www.ft.com/cms/s/2/4a35c0b2-636e-11e4-9a79-00144feabdc0.html |archive-url=https://ghostarchive.org/archive/20221210/http://www.ft.com/cms/s/2/4a35c0b2-636e-11e4-9a79-00144feabdc0.html |archive-date=10 December 2022 |url-access=subscription |url-status=live |title=Tech groups aid terror, says UK spy chief |author=Sam Jones and Murad Ahmed |newspaper=Financial Times |date=3 November 2014 |access-date=3 November 2014}}</ref> However the head of the UK technology industry group [[techUK]] rejected these claims, stating that they understood the issues but that disclosure obligations "must be based upon a clear and transparent legal framework and effective oversight rather than, as suggested, a deal between the industry and government".<ref name="telegraph-20141104">{{cite news |url=https://www.telegraph.co.uk/technology/11208999/Tech-giants-reject-GCHQ-boss-Robert-Hannigans-call-for-deal-with-government.html |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/technology/11208999/Tech-giants-reject-GCHQ-boss-Robert-Hannigans-call-for-deal-with-government.html |archive-date=12 January 2022 |url-access=subscription |url-status=live |title=Tech giants reject GCHQ boss Robert Hannigan's call for deal with government |author=David Barrett |newspaper=The Daily Telegraph |date=4 November 2014 |access-date=5 November 2014}}{{cbignore}}</ref>

In 2015, documents obtained by ''[[The Intercept]]'' from US [[National Security Agency]] whistleblower [[Edward Snowden]] revealed that GCHQ had carried out a mass-surveillance operation, codenamed [[Karma Police (surveillance program)|KARMA POLICE]], since about 2008.<ref name="Karma">Ryan Gallager, [https://theintercept.com/2015/09/25/gchq-radio-porn-spies-track-web-users-online-identities/ Profiled: From Radio to Porn, British Spies Track Web Users' Online Identities] {{Webarchive|url=https://web.archive.org/web/20210910193008/https://theintercept.com/2015/09/25/gchq-radio-porn-spies-track-web-users-online-identities/ |date=10 September 2021 }}, ''The Intercept'' (25 September 2015).</ref> The operation swept up the [[IP address]] of Internet users visiting websites, and was established with no public scrutiny or oversight. KARMA POLICE is a powerful spying tool in conjunction with other GCHQ programs because IP addresses could be cross-referenced with other data.<ref name="Karma"/> The goal of the program, according to the documents, was "either (a) a web browsing profile for every visible user on the internet, or (b) a user profile for every visible website on the internet."<ref name="Karma"/>

In 2015, GCHQ admitted for the first time in court that it conducts computer hacking.<ref>Croft, Jane (1 December 2015) [http://www.ft.com/cms/s/0/7e9d93b2-9832-11e5-9228-87e603d47bdc.html UK spy agency GCHQ admits it carries out computer hacking] {{Webarchive|url=https://web.archive.org/web/20151203223413/http://www.ft.com/cms/s/0/7e9d93b2-9832-11e5-9228-87e603d47bdc.html |date=3 December 2015 }}. ''Financial Times''</ref>

In 2017, US Press Secretary [[Sean Spicer]] made allegations that GCHQ had conducted surveillance on US President [[Donald Trump]]. These unfounded claims were based on statements made during an opinion piece in a FOX media segment.<ref>Farrell, Henry (16 March 2017) [https://www.washingtonpost.com/news/monkey-cage/wp/2017/03/16/sean-spicer-just-suggested-that-obama-used-british-intelligence-to-spy-on-trump-not-so-much/ Sean Spicer just suggested that Obama used British intelligence to spy on Trump. Not so much] {{Webarchive|url=https://web.archive.org/web/20170317020548/https://www.washingtonpost.com/news/monkey-cage/wp/2017/03/16/sean-spicer-just-suggested-that-obama-used-british-intelligence-to-spy-on-trump-not-so-much/ |date=17 March 2017 }}. ''The Washington Post''</ref><ref>Blake, Aaron (16 March 2017) [https://www.washingtonpost.com/news/the-fix/wp/2017/03/16/sean-spicers-angry-lonely-defense-of-trumps-wiretapping-claim-annotated/ Sean Spicer's angry, lonely defense of Trump's wiretapping claim, annotated] {{Webarchive|url=https://web.archive.org/web/20170317053939/https://www.washingtonpost.com/news/the-fix/wp/2017/03/16/sean-spicers-angry-lonely-defense-of-trumps-wiretapping-claim-annotated/ |date=17 March 2017 }}. ''The Washington Post''</ref> The US government formally apologised for the unfounded allegations and promised they would not be repeated.<ref>{{cite news|title=US makes formal apology to Britain after White House accuses GCHQ of wiretapping Trump Tower|url=https://www.telegraph.co.uk/news/2017/03/17/us-makes-formal-apology-britain-white-house-accuses-gchq-wiretapping/|access-date=17 March 2017|work=The Telegraph|date=17 March 2017|archive-date=22 March 2017|archive-url=https://web.archive.org/web/20170322064105/https://www.telegraph.co.uk/news/2017/03/17/us-makes-formal-apology-britain-white-house-accuses-gchq-wiretapping/|url-status=live}}</ref><ref>{{cite news|title=White House apologizes to British government over spying claims|url=https://edition.cnn.com/2017/03/17/politics/gchq-trump-wiretap-denial/|access-date=17 March 2017|publisher=CNN|date=17 December 2017|archive-date=18 March 2017|archive-url=https://web.archive.org/web/20170318003415/http://edition.cnn.com/2017/03/17/politics/gchq-trump-wiretap-denial/|url-status=live}}</ref><ref>{{cite news |url=https://www.theguardian.com/us-news/2017/mar/16/gchq-denies-wiretap-claim-trump-obama |title=GCHQ dismisses 'utterly ridiculous' claim it helped wiretap Trump &#124; US news |newspaper=The Guardian |access-date=13 April 2017 |date=17 March 2017 |archive-date=21 April 2019 |archive-url=https://web.archive.org/web/20190421154146/https://www.theguardian.com/us-news/2017/mar/16/gchq-denies-wiretap-claim-trump-obama |url-status=live }}</ref>

British intelligence did gather information relating to Russian [[Links between Trump associates and Russian officials and spies|contacts made by Trump's campaign team]] in the run-up to his election, which were passed on to US intelligence agencies.<ref>{{cite news |url=https://www.theguardian.com/uk-news/2017/apr/13/british-spies-first-to-spot-trump-team-links-russia |title=British spies were first to spot Trump team's links with Russia |newspaper=The Guardian |access-date=13 April 2017 |date=13 April 2017 |last1=Harding |first1=Luke |last2=Kirchgaessner |first2=Stephanie |last3=Hopkins |first3=Nick |archive-date=13 April 2017 |archive-url=https://web.archive.org/web/20170413135157/https://www.theguardian.com/uk-news/2017/apr/13/british-spies-first-to-spot-trump-team-links-russia |url-status=live }}</ref><ref>{{cite news|title=British intelligence passed Trump associates' communications with Russians on to US counterparts|url=https://edition.cnn.com/2017/04/13/politics/trump-russia-british-intelligence/index.html?sr=twpol041317trump-russia-british-intelligence0910PMVODtopLink&linkId=36496320|access-date=14 April 2017|publisher=CNN|date=14 April 2017|archive-date=15 April 2017|archive-url=https://web.archive.org/web/20170415200602/http://edition.cnn.com/2017/04/13/politics/trump-russia-british-intelligence/index.html?sr=twpol041317trump-russia-british-intelligence0910PMVODtopLink&linkId=36496320|url-status=live}}</ref>

On 31 October 2018, GCHQ joined [[Instagram]].<ref>{{Cite web|url=https://www.instagram.com/gchq/|title=GCHQ (@gchq) • Instagram photos and videos|website=www.instagram.com|language=en|access-date=1 November 2018|archive-date=14 May 2020|archive-url=https://web.archive.org/web/20200514145303/https://www.instagram.com/gchq/|url-status=live}}</ref><ref>{{Cite web|url=https://www.theguardian.com/uk-news/2018/oct/31/gchq-uses-instagram-to-open-up-secret-world-of-espionage-to-public|title=GCHQ uses Instagram to 'open up world of espionage' to public|last=Weaver|first=Matthew|date=31 October 2018|website=The Guardian|language=en|access-date=1 November 2018|archive-date=31 October 2018|archive-url=https://web.archive.org/web/20181031234851/https://www.theguardian.com/uk-news/2018/oct/31/gchq-uses-instagram-to-open-up-secret-world-of-espionage-to-public|url-status=live}}</ref>

==Personnel awards==
GCHQ personnel are recognised annually by [[King Charles III]] (formerly the Prince of Wales) at the [[Prince of Wales's Intelligence Community Awards]] at [[St James's Palace]] or [[Clarence House]] alongside members of the [[MI5|Security Service]] (MI5), and [[Secret Intelligence Service]] (MI6).<ref name="Mayer2016">{{cite book|last=Mayer|first=Catherine|title=Charles: the Heart of a King|publisher=[[Ebury Publishing]]|year=2016|isbn=978-0-7535-5595-8|url=https://books.google.com/books?id=ZpnACwAAQBAJ&pg=PA175|access-date=24 October 2021|page=175}}</ref> Awards and citations are given to teams within the agencies as well as individuals.<ref name="Mayer2016"/>

=={{Anchor|Security Mission}}{{Anchor|London Communications Security Agency}}Security mission==
As well as a mission to gather intelligence, GCHQ has for a long time had a corresponding mission to assist in the protection of the British government's own communications. When the Government Code and Cypher School (GC&CS) was created in 1919, its overt task was providing security advice.<ref name="natarchhistory">{{cite web|url=http://www.nationalarchives.gov.uk/documents/information-management/osp28.pdf |archive-url=https://web.archive.org/web/20110612121900/https://www.nationalarchives.gov.uk/documents/information-management/osp28.pdf |archive-date=2011-06-12 |url-status=live |title=Operational Selection Policy OSP8 |access-date=24 January 2018}}</ref> GC&CS's Security section was located in [[Mansfield College, Oxford]] during the Second World War.<ref name="natarchhistory"/>

In April 1946, GC&CS became GCHQ, and the now GCHQ Security section moved from Oxford to join the rest of the organisation at [[RAF Eastcote|Eastcote]] later that year.<ref name="natarchhistory"/>

===LCSA===
From 1952 to 1954, the intelligence mission of GCHQ relocated to Cheltenham; the Security section remained at Eastcote,<ref name="natarchhistory"/> and in March 1954 became a separate, independent organisation: the '''London Communications Security Agency''' (LCSA),<ref name="natarchhistory"/> which in 1958 was renamed to the '''London Communications-Electronic Security Agency''' (LCESA).<ref name="natarchhistory"/>

In April 1965, GPO and MOD units merged with LCESA to become the '''Communications-Electronic Security Department''' (CESD).<ref name="natarchhistory"/>

===CESG===
In October 1969, CESD was merged into GCHQ and becoming '''Communications-Electronic Security Group''' ('''CESG''').<ref name="natarchhistory"/>

In 1977 CESG relocated from Eastcote to Cheltenham.<ref name="natarchhistory"/>

CESG continued as the UK National Technical Authority for [[information assurance]], including [[cryptography]]. CESG did not manufacture security equipment, but worked with industry to ensure the availability of suitable products and services, while GCHQ itself funded research into such areas, for example to the [[Centre for Quantum Computation]] at [[Oxford University]] and the [[Heilbronn Institute for Mathematical Research]] at the [[University of Bristol]].<ref>{{cite web|url=http://www.maths.bristol.ac.uk/research/heilbronn_institute/|title=Heilbronn Institute for Mathematical Research|publisher=[[University of Bristol]]|access-date=30 August 2008|archive-date=22 February 2014|archive-url=https://web.archive.org/web/20140222145451/http://www.maths.bristol.ac.uk/research/heilbronn_institute/|url-status=live}}</ref>

In the 21st century, CESG ran a number of assurance schemes such as CHECK, [[CESG Listed Adviser Scheme|CLAS]], [[Commercial Product Assurance]] (CPA) and CESG Assisted Products Service (CAPS).<ref>{{cite web|url = https://www.cesg.gov.uk/servicecatalogue/Pages/index.aspx|access-date = 17 August 2015|title = CESG Service Catalogue|archive-url = https://web.archive.org/web/20150820011137/http://www.cesg.gov.uk/servicecatalogue/Pages/index.aspx|archive-date = 20 August 2015|url-status = dead}}</ref>

====Public key encryption====
In 1970 the concept for [[public-key encryption]] ([[public key infrastructure]]) was developed and proven by GCHQ's [[James H. Ellis]]. Ellis lacked the [[number theory]] skills required to build a workable system. In 1974 GCHQ mathematician [[Clifford Cocks]] had developed a workable public key cryptography algorithm and a workable PKI system. Cocks's system was not available in the public domain until it was [[declassified]] in 1997.<ref>{{cite web |last=Singh |first=Simon |author-link=Simon Singh |title=Unsung Heroes of Cryptography |url=http://simonsingh.net/media/articles/maths-and-science/unsung-heroes-of-cryptography/ |url-status=live |archive-url=https://web.archive.org/web/20141205012040/http://simonsingh.net/media/articles/maths-and-science/unsung-heroes-of-cryptography/ |archive-date=5 December 2014 |access-date=13 June 2012}} (Originally published in ''[[The Sunday Telegraph]]'')</ref><ref>{{Cite web |title=James Ellis |url=https://www.gchq.gov.uk/person/james-ellis |access-date=2023-11-17 |website=www.gchq.gov.uk |language=en}}</ref>

By 1997 broader public key cryptography commercial technologies had  been independently developed and had become well established, in areas such as [[email security]], [[digital signature]]s, and [[Transport Layer Security|TLS]] (a fundamental [[TCP/IP]] security component) etc.<ref>{{Cite web |title=Introduction to PKI |url=https://www.ncsc.gov.uk/collection/in-house-public-key-infrastructure/introduction-to-public-key-infrastructure |access-date=2023-11-16 |website=www.ncsc.gov.uk |language=en}}</ref> Most notably in 1977 the [[RSA (cryptosystem)|RSA]] algorithm had been developed (equivalent to Cocks's system) and by 1997 was extremely well established.<ref>{{Cite web |title=Prehistory of Public Key Cryptography |url=https://www.cs.columbia.edu/~smb/nsam-160/ |access-date=2023-11-16 |website=www.cs.columbia.edu}}</ref>

===NCSC===
In 2016, the [[National Cyber Security Centre (United Kingdom)|National Cyber Security Centre]] was established under GCHQ but located in London, as the UK's authority on cybersecurity. It absorbed and replaced CESG as well as activities that had previously existed outside GCHQ: the Centre for Cyber Assessment (CCA), Computer Emergency Response Team UK (CERT UK) and the cyber-related responsibilities of the [[Centre for the Protection of National Infrastructure]] (CPNI).<ref>{{cite web |author1=HM Government |date=1 November 2016 |title=National Cyber Security Strategy 2016-2021 |url=https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/564268/national_cyber_security_strategy.pdf |access-date=2 November 2016 |website=gov.uk |page=29 |archive-date=1 November 2016 |archive-url=https://web.archive.org/web/20161101141935/https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/564268/national_cyber_security_strategy.pdf |url-status=live }}</ref>

==Joint Technical Language Service==
The Joint Technical Language Service (JTLS) was established in 1955,<ref>{{cite book |url=https://books.google.com/books?id=8usCJVZY1vkC&pg=PA40 |title=About Translation |first=Peter |last=Newmark |year=1991 |isbn=1-85359-118-1 |publisher=Multilingual Matters |page=40}}</ref> drawing on members of the small Ministry of Defence technical language team and others, initially to provide standard English translations for organisational expressions in any foreign language, discover the correct English equivalents of technical terms in foreign languages and discover the correct expansions of abbreviations in any language.<ref>{{cite book|author=Joint Technical Language Service|title=Russian-English Military Dictionary|year=1983|publisher=The Stationery Office|isbn= 9780112300199|edition=English and Russian}}</ref> The remit of the JTLS has expanded in the ensuing years to cover technical language support and interpreting and translation services across the UK Government and to local public sector services in [[Gloucestershire]] and surrounding counties. The JTLS also produces and publishes foreign language working aids under [[crown copyright]] and conducts research into machine translation and on-line dictionaries and glossaries. The JTLS is co-located with GCHQ for administrative purposes.<ref>{{cite web|url=http://discovery.nationalarchives.gov.uk/details/r/C6814022|title=Government Communications Headquarters, Cheltenham; Joint Technical Language Service|publisher=National Archives|access-date=25 February 2018|archive-date=26 February 2018|archive-url=https://web.archive.org/web/20180226094057/http://discovery.nationalarchives.gov.uk/details/r/C6814022|url-status=live}}</ref>

==International relationships==
{{See also|UKUSA Agreement|Five Eyes}}
GCHQ operates in partnership with equivalent agencies worldwide in a number of bi-lateral and multi-lateral relationships. The principal of these is with the United States ([[National Security Agency]]), Canada ([[Communications Security Establishment]]), Australia ([[Australian Signals Directorate]]) and New Zealand ([[Government Communications Security Bureau]]), through the mechanism of the [[UK-US Security Agreement]], a broad intelligence-sharing agreement encompassing a range of intelligence collection methods. Relationships are alleged to include shared collection methods, such as the system described in the popular media as [[ECHELON]], as well as analysed product.<ref name=EP>{{cite web|url=https://fas.org/irp/program/process/rapport_echelon_en.pdf |archive-url=https://web.archive.org/web/20010920203747/http://www.fas.org/irp/program/process/rapport_echelon_en.pdf |archive-date=2001-09-20 |url-status=live|title=On the existence of a global system for the interception of private and commercial communications (ECHELON interception system) – Temporary Committee on the ECHELON Interception System, (2001/2098(INI))|last=Schmid|first=Gerhard|date=11 July 2001|page=194 |publisher=European Parliament: Temporary Committee on the ECHELON Interception System |access-date=27 March 2008}}</ref>

==Legal basis==

{{Main|Intelligence Services Act 1994}}

GCHQ's legal basis is established by the [[Intelligence Services Act 1994]] Section 3 as follows:

{{Blockquote|{{unbulleted list|item_style=margin-left:1.5em;text-indent:-1.5em
|(1) There shall continue to be a Government Communications Headquarters under the authority of the Secretary of State; and, subject to subsection (2) below, its functions shall be—{{unbulleted list|item_style=margin-left:1.5em;text-indent:-1.5em
|(a) to monitor or interfere with electromagnetic, acoustic and other emissions and any equipment producing such emissions and to obtain and provide information derived from or related to such emissions or equipment and from encrypted material; and
|(b) to provide advice and assistance about—{{unbulleted list|item_style=margin-left:1.5em;text-indent:-1.5em
|(i) languages, including terminology used for technical matters, and
|(ii) cryptography and other matters relating to the protection of information and other material, to the armed forces of the Crown, to Her Majesty's Government in the United Kingdom or to a Northern Ireland Department or to any other organisation which is determined for the purposes of this section in such manner as may be specified by the Prime Minister.}}}}
|(2) The functions referred to in subsection (1)(a) above shall be exercisable only—{{unbulleted list|item_style=margin-left:1.5em;text-indent:-1.5em
|(a) in the interests of national security, with particular reference to the defence and foreign policies of His Majesty's Government in the United Kingdom; or
|(b) in the interests of the economic well-being of the United Kingdom in relation to the actions or intentions of persons outside the British Islands; or
|(c) in support of the prevention or detection of serious crime.}}
|(3) In this Act, the expression "GCHQ" refers to the Government Communications Headquarters and to any unit or part of a unit of the armed forces of the Crown which is for the time being required by the Secretary of State to assist the Government Communications Headquarters in carrying out its functions.<ref name="InTel94"/>}}}}

Activities that involve interception of communications are permitted under the [[Regulation of Investigatory Powers Act 2000]]; this kind of interception can only be carried out after a warrant has been issued by a [[Secretary of State (United Kingdom)|Secretary of State]]. The [[Human Rights Act 1998]] requires the intelligence agencies, including GCHQ, to respect citizens' rights as described in the [[European Convention on Human Rights]].<ref name=GCHQlaw>{{cite web|title=The Law|url=http://www.gchq.gov.uk/how_we_work/running_the_business/oversight/Pages/The-law.aspx|publisher=GCHQ|access-date=17 December 2013|archive-date=13 January 2020|archive-url=https://web.archive.org/web/20200113191839/https://www.gchq.gov.uk/how_we_work/running_the_business/oversight/Pages/The-law.aspx|url-status=dead}}</ref><ref name=refBBC20141205>{{cite news|title=GCHQ does not breach human rights, judges rule|url=https://www.bbc.co.uk/news/uk-30345801|access-date=6 December 2014|publisher=BBC|date=5 December 2014|archive-date=7 March 2021|archive-url=https://web.archive.org/web/20210307231234/https://www.bbc.co.uk/news/uk-30345801|url-status=live}}</ref><ref>{{cite news|title=The Andrew Marr Show Interview: Theresa May, MP Home Secretary|url=http://news.bbc.co.uk/1/shared/bsp/hi/pdfs/2311201402.pdf |archive-url=https://web.archive.org/web/20141211054354/http://news.bbc.co.uk/1/shared/bsp/hi/pdfs/2311201402.pdf |archive-date=2014-12-11 |url-status=live|access-date=6 December 2014|publisher=BBC|date=23 November 2014|quote=Well I guess what he's talking about is the fact that for certain aspects and certain of the more intrusive measures that our security service and police have available to them – i.e. Intercept, intercepting people's telephones and some other intrusive measures – the decision is taken by the Secretary of State, predominantly me. A significant part of my job is looking at these warrants and signing these warrants. I think it's... Some people argue that should be to judges....I think it's very important that actually those decisions are being taken by somebody who is democratically accountable to the public. I think that's an important part of our system. I think it's a strength of our system.}}</ref>

===Oversight===
{{See also|Mass surveillance in the United Kingdom}}

The [[Prime Minister of the United Kingdom|Prime Minister]] nominates cross-party [[Parliament of the United Kingdom|Members of Parliament]] to an [[Intelligence and Security Committee]]. The remit of the Committee includes oversight of intelligence and security activities and reports are made directly to Parliament.<ref name="ISC" /> Its functions were increased under the [[Justice and Security Act 2013]] to provide for further access and investigatory powers.<ref>{{cite web|url=https://www.legislation.gov.uk/ukpga/2013/18/body|title=Justice and Security Act 2013|publisher=Legislation.co.uk|access-date=8 December 2021|archive-date=8 December 2021|archive-url=https://web.archive.org/web/20211208104659/https://www.legislation.gov.uk/ukpga/2013/18/body|url-status=live}}</ref>

Judicial oversight of GCHQ's conduct is exercised by the [[Investigatory Powers Tribunal]].<ref>{{cite web|title=Functions – Key role|url=http://www.ipt-uk.com/section.aspx?pageid=1|publisher=The Investigatory Powers Tribunal|access-date=6 February 2015|url-status=dead|archive-url=https://web.archive.org/web/20150206141009/http://www.ipt-uk.com/section.aspx?pageid=1|archive-date=6 February 2015}}</ref> The UK also has an independent [[Intelligence Services Commissioner]] and Interception of Communications Commissioner, both of whom are former senior judges.<ref>{{cite web|url=http://www.intelligencecommissioners.com/|title=Intelligence Commissioners|access-date=14 December 2013|archive-date=7 January 2014|archive-url=https://web.archive.org/web/20140107042445/http://www.intelligencecommissioners.com/|url-status=dead}}</ref>

The Investigatory Powers Tribunal ruled in December 2014 that GCHQ does not breach the [[European Convention on Human Rights]], and that its activities are compliant with Articles 8 (right to privacy) and 10 (freedom of expression) of the European Convention on Human Rights.<ref name=refBBC20141205 /> However, the Tribunal stated in February 2015 that one particular aspect, the data-sharing arrangement that allowed UK Intelligence services to request data from the US surveillance programmes [[PRISM (surveillance program)|Prism]] and [[Upstream collection|Upstream]], had been in contravention of human rights law prior to this until two paragraphs of additional information, providing details about the procedures and safeguards, were disclosed to the public in December 2014.<ref>{{cite web|title=IPT Ruling on Interception|url=http://www.gchq.gov.uk/press_and_media/news_and_features/Pages/IPT-Ruling-on-Interception-Feb-2014.aspx|publisher=GCHQ|access-date=6 February 2015|url-status=dead|archive-url=https://web.archive.org/web/20150206205536/http://www.gchq.gov.uk/press_and_media/news_and_features/Pages/IPT-Ruling-on-Interception-Feb-2014.aspx|archive-date=6 February 2015}}</ref><ref>{{cite news|title=GCHQ censured over sharing of internet surveillance data with US|url=https://www.bbc.com/news/uk-31164451|access-date=6 February 2015|publisher=BBC|date=6 February 2015|archive-date=7 February 2015|archive-url=https://web.archive.org/web/20150207092353/http://www.bbc.com/news/uk-31164451|url-status=live}}</ref><ref>{{cite news|title=UK-US surveillance regime was unlawful 'for seven years'|url=https://www.theguardian.com/uk-news/2015/feb/06/gchq-mass-internet-surveillance-unlawful-court-nsa|access-date=6 February 2015|work=The Guardian|date=6 February 2015|archive-date=6 February 2015|archive-url=https://web.archive.org/web/20150206115924/http://www.theguardian.com/uk-news/2015/feb/06/gchq-mass-internet-surveillance-unlawful-court-nsa|url-status=live}}</ref>

Furthermore, the IPT ruled that the legislative framework in the United Kingdom does not permit [[mass surveillance]] and that while GCHQ collects and analyses data in bulk, it does not practice mass surveillance.<ref name=refBBC20141205 /><ref>{{cite web|title=IPT rejects assertions of mass surveillance|url=http://www.gchq.gov.uk/press_and_media/news_and_features/Pages/IPT-rejects-assertions-of-mass-surveillance.aspx|publisher=GCHQ|access-date=7 February 2015|date=5 December 2014|archive-url=https://web.archive.org/web/20150206232713/http://www.gchq.gov.uk/press_and_media/news_and_features/Pages/IPT-rejects-assertions-of-mass-surveillance.aspx|archive-date=6 February 2015|url-status=dead}}</ref><ref>{{cite web|title=List of judgments|url=http://www.ipt-uk.com/section.aspx?pageid=8|publisher=Investigatory Powers Tribunal|access-date=7 February 2015|date=5 December 2014|quote=1. A declaration that the regime governing the soliciting, receiving, storing and transmitting by UK authorities of private communications of individuals located in the UK which have been obtained by US authorities pursuant to Prism and/or Upstream does not contravene Articles 8 or 10 ECHR. 2. A declaration that the regime in respect of interception under ss8(4), 15 and 16 of the Regulation of investigatory Powers Act 2000 does not contravene Articles 8 or 10 ECHR and does not give rise to unlawful discrimination contrary to Article 14, read together with Articles 8 and/or 10 of the ECHR.|url-status=dead|archive-url=https://web.archive.org/web/20150206211011/http://www.ipt-uk.com/section.aspx?pageid=8|archive-date=6 February 2015}}</ref> This complements independent reports by the Interception of Communications Commissioner,<ref>{{cite web|title=Statement by the Interception of Communications Commissioner's Office (IOCCO) on the publication of the Interception of Communications Commissioner's Report 2014|url=http://www.iocco-uk.info/docs/2015%20Press%20Release%20Final.pdf|access-date=14 March 2015|date=12 March 2015|archive-url=https://web.archive.org/web/20150402112439/http://www.iocco-uk.info/docs/2015%20Press%20Release%20Final.pdf|archive-date=2 April 2015|url-status=dead}}{{cite web|title=Report of the Interception of Communications Commissioner|url=http://www.iocco-uk.info/docs/IOCCO%20Report%20March%202015%20(Web).pdf|access-date=14 March 2015|date=March 2015|archive-url=https://web.archive.org/web/20150321204956/http://www.iocco-uk.info/docs/IOCCO%20Report%20March%202015%20(Web).pdf|archive-date=21 March 2015|url-status=dead}}</ref> and a special report made by the Intelligence and Security Committee of Parliament; although several shortcomings and potential improvements to both oversight and the legislative framework were highlighted.<ref>{{cite web|title=Privacy and Security: A modern and transparent legal framework|url=http://isc.independent.gov.uk/news-archive/12march2015|publisher=Intelligence and Security Committee of Parliament|access-date=14 March 2015|date=12 March 2015|archive-date=16 March 2015|archive-url=https://web.archive.org/web/20150316093647/http://isc.independent.gov.uk/news-archive/12march2015|url-status=dead}}{{cite web|title=UK surveillance 'lacks transparency', ISC report says|url=https://www.bbc.co.uk/news/uk-31845338|publisher=BBC|access-date=14 March 2015|date=12 March 2015|archive-date=8 March 2021|archive-url=https://web.archive.org/web/20210308034530/https://www.bbc.co.uk/news/uk-31845338|url-status=live}}{{cite news|title=Intelligence and security committee report: the key findings|url=https://www.theguardian.com/world/2015/mar/12/intelligence-security-committee-report-key-findings|access-date=14 March 2015|work=The Guardian|date=12 March 2015|archive-date=8 March 2021|archive-url=https://web.archive.org/web/20210308180804/https://www.theguardian.com/world/2015/mar/12/intelligence-security-committee-report-key-findings|url-status=live}}</ref>

===Abuses===

Despite the inherent secrecy around much of GCHQ's work, investigations carried out by the UK government after the Snowden disclosures have admitted various abuses by the security services.  A report by the [[Intelligence and Security Committee]] (ISC) in 2015 revealed that a small number of staff at UK intelligence agencies had been found to misuse their surveillance powers, in one case leading to the dismissal of a member of staff at GCHQ, although there were no laws in place at the time to make these abuses a criminal offence.<ref>{{cite news|title=Handful of UK spies accessed private information inappropriately, ISC says|url=https://www.theguardian.com/world/2015/mar/12/handful-of-uk-spies-accessed-private-information-inappropriately-isc-says|access-date=31 December 2016|work=The Guardian|date=12 March 2015|archive-date=1 January 2017|archive-url=https://web.archive.org/web/20170101003506/https://www.theguardian.com/world/2015/mar/12/handful-of-uk-spies-accessed-private-information-inappropriately-isc-says|url-status=live}}</ref>

Later that year, a ruling by the [[Investigatory Powers Tribunal]] found that GCHQ acted unlawfully in conducting surveillance on two human rights organisations. The closed hearing found the government in breach of its internal surveillance policies in accessing and retaining the communications of the [[Egyptian Initiative for Personal Rights]] and the [[Legal Resources Centre]] in South Africa. This was only the second time in the IPT's history that it had made a positive determination in favour of applicants after a closed session.<ref>{{cite web|title=UK: Unlawful spying on two organisations reinforces need for intelligence services to end mass surveillance|url=https://www.amnesty.org.uk/press-releases/uk-unlawful-spying-two-organisations-reinforces-need-intelligence-services-end-mass|publisher=[[Amnesty International UK]]|access-date=31 December 2016|date=22 June 2015|archive-date=20 January 2017|archive-url=https://web.archive.org/web/20170120172838/https://www.amnesty.org.uk/press-releases/uk-unlawful-spying-two-organisations-reinforces-need-intelligence-services-end-mass|url-status=live}}</ref>

At another IPT case in 2015, GCHQ conceded that "from January 2010, the regime for the interception/obtaining, analysis, use, disclosure and destruction of legally privileged material has not been in accordance with the law for the purposes of Article 8(2) of the European convention on human rights and was accordingly unlawful".<ref>{{cite web|title=Case No. IPT/13/132-9/H IN THE INVESTIGATORY POWERS TRIBUNAL|url=http://www.ipt-uk.com/docs/Belhadj_order_26Feb15.pdf |archive-url=https://web.archive.org/web/20150426141903/http://www.ipt-uk.com/docs/Belhadj_order_26Feb15.pdf |archive-date=2015-04-26 |url-status=live|publisher=The [[Investigatory Powers Tribunal]]|access-date=31 December 2016|date=26 February 2015}}</ref> This admission was made in connection with a case brought against them by [[Abdelhakim Belhaj]], a Libyan opponent of the former Gaddafi regime, and his wife Fatima Bouchard. The couple accused British ministers and officials of participating in their unlawful abduction, kidnapping and removal to Libya in March 2004, while Gaddafi was still in power.<ref>{{cite news|title=Legal privilege and the conflicting interests of GCHQ and the IPT|url=https://www.theguardian.com/law/2015/mar/16/legal-privilege-conflicting-interests-gchq-ipt-investigatory-powers-tribunal|access-date=31 December 2016|work=The Guardian|date=16 March 2015|archive-date=1 January 2017|archive-url=https://web.archive.org/web/20170101004744/https://www.theguardian.com/law/2015/mar/16/legal-privilege-conflicting-interests-gchq-ipt-investigatory-powers-tribunal|url-status=live}}</ref>

On 25 May 2021, the European Court of Human Rights (ECHR) ruled that the GCHQ is guilty of violating data privacy rules through their bulk interception of communications, and does not provide sufficient protections for confidential journalistic material because it gathers communications in bulk.<ref>{{Cite web|date=25 May 2021|title=EU Human Rights Court Finds UK's Intelligence Agency GCHQ Guilty of Violating Privacy Laws {{!}} 25 May 2021|url=https://dailynewsbrief.com/2021/05/25/eu-human-rights-court-finds-uks-intelligence-agency-gchq-guilty-of-violating-privacy-laws/|access-date=25 May 2021|website=The Daily NewsBrief|language=en-US|archive-date=25 May 2021|archive-url=https://web.archive.org/web/20210525222626/https://dailynewsbrief.com/2021/05/25/eu-human-rights-court-finds-uks-intelligence-agency-gchq-guilty-of-violating-privacy-laws/|url-status=live}}</ref>

====Surveillance of parliamentarians====
In 2015 there was a complaint by [[Green Party of England and Wales|Green Party]] MP [[Caroline Lucas]] that British intelligence services, including GCHQ, had been spying on MPs allegedly "in defiance of laws prohibiting it."<ref>{{cite news|title=British intelligence service spying on MPs in defiance of laws prohibiting it|url=https://www.independent.co.uk/news/uk/politics/british-intelligence-service-spying-on-mps-in-defiance-of-laws-prohibiting-it-10411996.html|access-date=31 December 2016|work=The Independent|date=23 July 2015|archive-date=1 January 2017|archive-url=https://web.archive.org/web/20170101005409/http://www.independent.co.uk/news/uk/politics/british-intelligence-service-spying-on-mps-in-defiance-of-laws-prohibiting-it-10411996.html|url-status=live}}</ref>

Then-[[Home Secretary]], [[Theresa May]], had told Parliament in 2014 that:
{{blockquote|Obviously, the [[Wilson Doctrine]] applies to parliamentarians. It does not absolutely exclude the use of these powers against parliamentarians, but it sets certain requirements for those powers to be used in relation to a parliamentarian. It is not the case that parliamentarians are excluded and nobody else in the country is, but there is a certain set of rules and protocols that have to be met if there is a requirement to use any of these powers against a parliamentarian.<ref>{{cite web|title=Daily Hansard – Debate, 15 July 2014 : Column 697|url=https://publications.parliament.uk/pa/cm201415/cmhansrd/cm140715/debtext/140715-0002.htm#14071547001384|publisher=[[Parliament of the United Kingdom]]|access-date=31 December 2016|date=15 July 2014|archive-date=25 October 2016|archive-url=https://web.archive.org/web/20161025201820/http://www.publications.parliament.uk/pa/cm201415/cmhansrd/cm140715/debtext/140715-0002.htm#14071547001384|url-status=live}}</ref>}}

The [[Investigatory Powers Tribunal]] investigated the complaint, and ruled that contrary to the allegation, there was no law that gave the communications of Parliament any special protection.<ref name=HuffPo>{{cite news|url=http://www.huffingtonpost.co.uk/2015/10/14/gchq-can-monitor-communic_n_8292390.html|title=GCHQ Can Monitor Communications Of MPs And Peers Rules Tribunal|newspaper=Huffington Post|author=Thomas Tamblyn|date=14 October 2015|access-date=24 January 2018|archive-date=25 January 2018|archive-url=https://web.archive.org/web/20180125015857/http://www.huffingtonpost.co.uk/2015/10/14/gchq-can-monitor-communic_n_8292390.html|url-status=live}}</ref> The Wilson Doctrine merely acts as a [[political convention]].<ref>{{cite web|url=http://www.ipt-uk.com/docs/Caroline_Lucas_JUDGMENT.pdf |archive-url=https://web.archive.org/web/20160317124014/http://www.ipt-uk.com/docs/Caroline_Lucas_JUDGMENT.pdf |archive-date=2016-03-17 |url-status=live|title=Approved Judgment|publisher=Investigatory Powers Tribunal|access-date=24 January 2018}}</ref>

==Constitutional legal case==
A controversial GCHQ case determined the scope of judicial review of prerogative powers (the Crown's residual powers under common law). This was ''[[Council of Civil Service Unions v Minister for the Civil Service]]'' [1985] AC 374 (often known simply as the "GCHQ case"). In this case, a prerogative Order in Council had been used by the prime minister (who is the [[Minister for the Civil Service]]) to ban trade union activities by civil servants working at GCHQ. This order was issued without consultation. The House of Lords had to decide whether this was reviewable by [[judicial review]]. It was held that executive action is not immune from judicial review simply because it uses powers derived from common law rather than statute (thus the prerogative is reviewable).<ref>{{cite BAILII |litigants=Council of Civil Service Unions v Minister for the Civil Service |link=Council of Civil Service Unions v Minister for the Civil Service |court=UKHL |division= |year=1984 |num=9 |parallelcite=[1985] ICR 14, [1985] IRLR 28, [1984] 3 WLR 1174, [1984] 3 All ER 935, [1985] AC 374 |date=22 November 1984 |courtname=auto}}</ref>

==Leadership==
{{Main|Director of the Government Communications Headquarters}}
The following is a list of the heads and operational heads of GCHQ and GC&CS:

*Sir [[Hugh Sinclair]] (1919–1939) (founder)
*Cmdr [[Alastair Denniston]] (1921–February 1942) (operational head)
*Sir [[Edward Travis]] (February 1942 – 1952)
*Sir [[Eric Malcolm Jones|Eric Jones]] (April 1952 – 1960)
*Sir [[Clive Loehnis]] (1960–1964)
*Sir [[Leonard Hooper]] (1965–1973)
*Sir [[Arthur Bonsall]] (1973–1978)
*Sir [[Brian Tovey|Brian John Maynard Tovey]] (1978–1983)
*Sir [[Peter Marychurch]] (1983–1989)
*Sir [[John Adye|John Anthony Adye]] (1989–1996)
*Sir [[David Omand]] (1996 –1997)
*Sir [[Kevin Tebbit]] (1998)
*Sir [[Francis Richards (diplomat)|Francis Richards]] (1998–2003)
*Sir [[David Pepper (intelligence official)|David Pepper]] (2003–2008)
*Sir [[Iain Lobban]] (2008–2014)
*[[Robert Hannigan]] (2014–2017)
*Sir [[Jeremy Fleming]] (2017–2023)
*[[Anne Keast-Butler]] (2023–Present)

==Stations and former stations==
The following are stations and former stations that have operated since the [[Cold War]].<ref>{{Cite web|url=https://www.gchq-careers.co.uk/life-at-gchq.html|title=Life at GCHQ {{!}} GCHQ|website=www.gchq-careers.co.uk|access-date=5 April 2019|archive-date=17 December 2019|archive-url=https://web.archive.org/web/20191217194156/https://gchq-careers.co.uk/life-at-gchq.html|url-status=live}}</ref><ref>{{cite web|url=https://books.google.com/books?id=2jCbW82ABTkC&pg=PA8|title=How Cheltenham entered America's backyard|date=5 April 1984|work=New Scientist|access-date=12 December 2014}}</ref>
{{col-begin}}
{{col-break}}

=== Current ===
====United Kingdom====

*[[GCHQ Bude]], Cornwall
*[[The Doughnut|GCHQ Cheltenham]], Gloucestershire (headquarters)
*GCHQ London
*GCHQ Manchester
*[[GCHQ Scarborough]], North Yorkshire
*[[RAF Digby]], Lincolnshire
*[[RAF Menwith Hill]], North Yorkshire

====Overseas====
* [[Cat Hill, Ascension Island|GCHQ Ascension Island]]
* [[Ayios Nikolaos Station|GCHQ Cyprus]]
* GCHQ [[Oman]]
{{col-break}}

=== Former ===
====United Kingdom====
*[[Brora Y Station|GCHQ Brora]], Sutherland
*[[GCHQ Cheadle]], Staffordshire
*[[RAF Culmhead|GCHQ Culmhead]], Somerset
*[[Hawklaw Y Station|GCHQ Hawklaw]], Fife

====Overseas====
====Hong Kong====
* GCHQ [[RAF Little Sai Wan]]
* GCHQ [[Chung Hom Kok]] (KITTIWAKE)
{{col-end}}

== In popular culture ==

In the historical drama film ''[[The Imitation Game]]'' (2014) [[Benedict Cumberbatch]] portrays [[Alan Turing]] in his efforts to break the Enigma code while employed by the Government Code and Cypher School.<ref>{{cite news|url=https://www.theguardian.com/film/2014/nov/15/benedict-cumberbatch-imitation-game-bletchley-park|title=Benedict Cumberbatch to inspire the next generation of codebreakers|last=Thorpe|first=Vanessa|date=15 November 2014|work=The Observer|access-date=6 December 2014|archive-date=3 December 2014|archive-url=https://web.archive.org/web/20141203191423/http://www.theguardian.com/film/2014/nov/15/benedict-cumberbatch-imitation-game-bletchley-park|url-status=live}}</ref>

GCHQ have set a number of cryptic online challenges to the public, used to attract interest and for recruitment, starting in late 1999.<ref>{{cite news|url=http://news.bbc.co.uk/1/hi/uk/601960.stm|title=Puzzling entrance to world of spies|work=[[BBC News]]|date= 13 January 2000}}</ref><ref>{{cite news|url=http://abcnews.go.com:80/sections/world/DailyNews/britspy000114.html|archive-url=https://web.archive.org/web/20010522053526/http://abcnews.go.com/sections/world/DailyNews/britspy000114.html|url-status=dead|archive-date=22 May 2001|title=The Spy Who Solved Me|date=15 January 2000|author=Caroline Byrne|work=[[ABC News (United States)|ABC News]]|access-date=12 March 2021}}</ref> The response to the 2004 challenge was described as "excellent",<ref>{{cite news|url=http://news.bbc.co.uk/1/hi/england/gloucestershire/3877907.stm|title=Huge response to spy base puzzle|work=[[BBC News]]|date= 10 July 2004}}</ref> and the challenge set in 2015 had over 600,000 attempts.<ref>{{cite news|url=https://www.telegraph.co.uk/news/uknews/12141189/GCHQ-quiz-solution-the-full-answers-but-can-you-understand-them.html |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/news/uknews/12141189/GCHQ-quiz-solution-the-full-answers-but-can-you-understand-them.html |archive-date=12 January 2022 |url-access=subscription |url-status=live|title=GCHQ quiz solution: the full answers – but can you understand them?|newspaper=[[The Daily Telegraph]]|date=4 February 2016|author=Gordon Rayner}}{{cbignore}}</ref> It also published the ''GCHQ Puzzle Book'' in 2016 which sold more than 300,000 copies, with the proceeds going to charity. A second book was published in October 2018.<ref>{{cite news|url=https://www.theguardian.com/uk-news/2018/aug/03/i-spy-another-fiendishly-difficult-gchq-puzzle-book|title=I spy ... another fiendishly difficult GCHQ puzzle book|date=3 August 2018|author=Ewen MacAskill|newspaper=[[The Guardian]]|access-date=20 January 2019|archive-date=21 January 2019|archive-url=https://web.archive.org/web/20190121064748/https://www.theguardian.com/uk-news/2018/aug/03/i-spy-another-fiendishly-difficult-gchq-puzzle-book|url-status=live}}</ref>

GCHQ appeared in the ''[[Doctor Who]]'' 2019 special "[[Resolution (Doctor Who)|Resolution]]" where the [[Dalek variants#Reconnaissance Scout Daleks|Reconnaissance Scout Dalek]] storms the facility and exterminates the staff in order to use the organisation's resources to summon a [[Dalek]] fleet.<ref>{{cite web|url=https://screenrant.com/doctor-who-dalek-gchq-response/|title=The U.K. Government's GCHQ has issued an official response to the Dalek attack in the Doctor Who New Year Special – no need to panic!|work=[[Screen Rant]]|last=Bacon|first=Thomas|date=2 January 2019|access-date=15 February 2020|archive-date=15 February 2020|archive-url=https://web.archive.org/web/20200215023706/https://screenrant.com/doctor-who-dalek-gchq-response/|url-status=live}}</ref><ref>{{cite web|url=https://www.slashfilm.com/doctor-who-resolution-review/|title='Resolution' Proves All the New 'Doctor Who' Needed Was an Old Villain|work=[[/Film]]|last=Bui|first=Hoai-Tran|date=2 January 2019|access-date=15 February 2020|archive-date=15 February 2020|archive-url=https://web.archive.org/web/20200215023704/https://www.slashfilm.com/doctor-who-resolution-review/|url-status=live}}</ref>

GCHQ is the setting of the 2020 [[Sky One]] sitcom ''[[Intelligence (British TV series)|Intelligence]]'', featuring [[David Schwimmer]] as an incompetent American [[NSA]] officer liaising with GCHQ's Cyber Crimes unit.<ref>{{cite web|url=https://www.soglos.com/music/48347/GCHQ-sitcom-Intelligence-starring-David-Schwimmer-airs-on-Sky-One|title=GCHQ sitcom Intelligence starring David Schwimmer airs on Sky One|publisher=So Glos|date=3 September 2020|access-date=3 September 2020|archive-date=28 September 2020|archive-url=https://web.archive.org/web/20200928165315/https://www.soglos.com/music/48347/GCHQ-sitcom-Intelligence-starring-David-Schwimmer-airs-on-Sky-One|url-status=live}}</ref>

In October 2020, intelligence and security expert John Ferris published [[Behind the Enigma|''Behind the Enigma: The Authorised History of GCHQ, Britain's Secret Cyber-Intelligence Agency''.]]<ref>{{Cite web |title=GCHQ's history told for the first time in Behind the Enigma |url=https://www.gchq.gov.uk/news/gchq-s-history-told-for-the-first-time-in-behind-the-enigma |access-date=2023-03-08 |website=www.gchq.gov.uk |language=en |archive-date=25 March 2023 |archive-url=https://web.archive.org/web/20230325094002/https://www.gchq.gov.uk/news/gchq-s-history-told-for-the-first-time-in-behind-the-enigma |url-status=live }}</ref>

GCHQ is the setting of the 2022 [[Channel 4]] drama ''[[The Undeclared War]]''. Set in the near future, it depicts a work experience student at the government agency during a cyberattack on the UK and the implications.<ref>{{cite news|url=https://www.radiotimes.com/tv/drama/undeclared-war-first-look-simon-pegg-exclusive-newsupdate/|title=The Undeclared War first look teases tense Simon Pegg and Mark Rylance series|first=Lauren|last=Morris|date=15 June 2022|accessdate=16 June 2022|website=[[RadioTimes.com]]|archive-date=15 June 2022|archive-url=https://web.archive.org/web/20220615145720/https://www.radiotimes.com/tv/drama/undeclared-war-first-look-simon-pegg-exclusive-newsupdate/|url-status=live}}</ref>

==See also==
GCHQ units:

* [[Joint Operations Cell]]
* [[National Cyber Security Centre (United Kingdom)|National Cyber Security Centre]]

GCHQ specifics:

*[[Capenhurst]] – said to be home to a GCHQ monitoring site in the 1990s
*[[Conel Hugh O'Donel Alexander|Hugh Alexander]] – head of the cryptanalysis division at GCHQ from 1949 to 1971
*[[Operation Socialist]], a 2010–2013 operation in Belgium
*[[Zircon (satellite)|Zircon]], the cancelled 1980s GCHQ satellite project

UK agencies:

*[[British intelligence agencies]]
*[[Joint Forces Intelligence Group]]
*[[RAF Intelligence]]
*[[UK cyber security community]]

Elsewhere:

*[[Signals intelligence by alliances, nations and industries]]
*[[NSA]] – equivalent United States organisation

==Notes and references==
{{Reflist|30em}}

==Bibliography==
* {{cite book |first=Richard J. |last=Aldrich |title=GCHQ: The Uncensored Story of Britain's Most Secret Intelligence Agency |publisher=HarperCollins |year=2010 |isbn=978-0007278473 }}
* {{cite book |first=John |last=Ferris |title=Behind the Enigma: The Authorised History of GCHQ |publisher=Bloomsbury |year=2020 |isbn=978-1-5266-0546-7}}
*{{cite book |first=John |last=Johnson |title=The Evolution of British Sigint: 1653–1939 |year=1997 |publisher=HMSO |asin=B002ALSXTC}}
*{{cite book |first=David |last=Kahn |title=Seizing the Enigma: The Race to Break the German U-Boats Codes, 1939–1943 |publisher=Houghton Mifflin |year=1991 |isbn=978-0395427392}}
*{{cite book |first=Michael |last=Smith |chapter=GC&CS and the First Cold War |title=Action This Day: Bletchley Park from the Breaking of the Enigma Code to the Birth of the Modern Computer |editor1-first=Michael |editor1-last=Smith |editor2-first=Ralph| editor2-last=Erskine |publisher=Bantam Press |year=2001 |isbn=978-0593049105}}

==External links==
{{Commons category|Government Communications Headquarters}}
* {{Official website}}
* [http://www.hmgcc.gov.uk His Majesty's Government Communications Centre]
* [https://web.archive.org/web/20070310181333/http://www.govcertuk.gov.uk/ GovCertUK]
* [http://www2.warwick.ac.uk/fac/soc/pais/people/aldrich/vigilant/lectures/gchq/ GCHQ: Britain's Most Secret Intelligence Agency]
* [https://www.bbc.co.uk/news/uk-england-gloucestershire-16290383 BBC: A final look at GCHQ's top secret Oakley site in Cheltenham]
* [http://electrospaces.blogspot.com/2014/11/incenser-or-how-nsa-and-gchq-are.html INCENSER, or how NSA and GCHQ are tapping internet cables]
* [https://www.bbc.co.uk/programmes/w3ct03lr The Secret History of GCHQ] BBC documentary

{{UK Intelligence Agencies}}
{{Foreign, Commonwealth and Development Office}}
{{Signals intelligence agencies}}
{{Five Eyes}}
{{Authority control}}
{{Portal bar|United Kingdom}}

[[Category:GCHQ| ]]
[[Category:1946 establishments in the United Kingdom]]
[[Category:British intelligence agencies]]
[[Category:Computer security organizations]]
[[Category:Cryptography organizations]]
[[Category:Foreign relations of the United Kingdom]]
[[Category:Government agencies established in 1946]]
[[Category:Organisations based in Cheltenham]]
[[Category:Signals intelligence agencies]]
[[Category:Organizations associated with Russian interference in the 2016 United States elections]]
[[Category:Headquarters in the United Kingdom]]