View source for 020

{{Short description|Dialling code for London in the United Kingdom}}
{{about|the United Kingdom telephone area code for London|the Netherlands area code|Telephone numbers in the Netherlands}}

{{Use British English|date=January 2014}}
{{Use dmy dates|date=November 2019}}
{{Infobox telephone area code
| trunk_code           = 0
| area_code            = 20
| area_name            = London
| number_format        = 020 xxxx xxxx
| locator_map          = {{location map|United Kingdom|label=020|lat=51.5155|long=-0.0922|caption=|float=}}
| coverage_map         = [[File:020 UK dial code area - 2007.png|230px]]Approximate coverage of 020 code (red), compared to Greater London boundary (black)
| coverage_map_caption = 
| country              = United Kingdom
| code_descriptor      = area code
| country_calling_code = 44
| conservation         = No
| active_date          = [[Big Number Change|1 June 1999]]<ref group="notes" name="020 date" />
| previous_codes       = 0171, 0181
| earlier_codes        = 01; 071, 081
| area_served          = [[Bushey Heath]]<br />[[Chigwell]]<br />[[Elstree]]<br />[[Ewell]]<br />London<br />[[Loughton]]<br />[[Thames Ditton]]
| codes_list           = List of dialling codes in the United Kingdom
}}
'''020''' is the [[Telephone numbers in the United Kingdom|national dialling code]] for London in the United Kingdom. All subscriber numbers within the area code consist of eight digits and it has capacity for approaching 100 million telephone numbers. The code is used at [[List of telephone exchanges in London|170 telephone exchanges]] in and around Greater London as part of the largest [[linked numbering scheme]] in the United Kingdom. In common with all other British area codes the initial '0' is a [[trunk prefix]] that is not required when dialling London from abroad.

The 020 area code fully replaced older area codes for London on 22 April 2000, following multiple telephone number changes during the 1990s.<ref group="notes" name="020 date">020 could be used from 1 June 1999 and the previous 0171 and 0181 codes could no longer be used from 22 April 2000.</ref>

As is the case for other codes in the UK, the 020 area code may also be used for services without any physical presence in the area, such as private networks or virtual numbering.<ref>{{Cite web|date=4 January 2021|title=The National Telephone Numbering Plan|url=https://www.ofcom.org.uk/__data/assets/pdf_file/0013/102613/national-numbering-plan.pdf|url-status=live|website=ofcom.org.uk|archive-url=https://web.archive.org/web/20180623113229/https://www.ofcom.org.uk/__data/assets/pdf_file/0013/102613/national-numbering-plan.pdf |archive-date=23 June 2018 }}</ref> One such user is the [[Foreign and Commonwealth Office]] Telecommunications Network, provided by [[Global Crossing]],{{Update inline|date=May 2023|?=yes|reason=Is the brand name Global Crossing still used by Lumen}} 020 is also one of the dialling codes used for telephone services on the remote South Atlantic island of [[Tristan da Cunha]].<ref>{{cite web|url=http://www.telecompaper.com/news/global-crossing-extends-fco-network-to-tristan-da-cunha--518367|title=Global Crossing extends FCO network to Tristan da Cunha|access-date=14 August 2015}}</ref>

==History==

===London telephone area===
Before the introduction of national dialling codes, the area now served by 020 had a large multiple telephone exchange system, called the London telephone area. The first exchange in this area, Central, was opened in the [[City of London]] on 1 March 1902.<ref name="BT 1902">{{cite web | url=http://www.btplc.com/mobile/Thegroup/BTsHistory/1881to1911/1902.htm | title=Events in Telecommunications History: 1902 | publisher=British Telecommunications PLC | archive-url=https://web.archive.org/web/20131212133246/http://www.btplc.com/mobile/Thegroup/BTsHistory/1881to1911/1902.htm | archive-date=12 December 2013 | url-status=live }}</ref> The [[Director telephone system]] was developed so that subscribers in London could call one another in a [[linked numbering scheme]] regardless of whether they were on a manual local exchange or an automatic one.

In 1927, Holborn, the first [[Director telephone system|Director]] automatic exchange in London, was cut over to the new system at midnight on Saturday 12 November. Because it was mainly a business exchange, most subscribers did not use the new system until Monday 14 November. The successful changeover was delayed by subscribers' unfamiliarity with dialling. Bishopgate and Sloane exchanges followed in six weeks, after which came Western and Monument exchanges. Because the London area contained 80 exchanges, complete conversion took many years.<ref name="Times 1927">The Times (London), 1927; 14 November p9 & 16 November p9</ref><ref name="Chapuis">{{cite book | title=100 Years of Telephone Switching: Manual and Electromechanical Switching (1878–1960s) Pt. 1  | year=2003 | author=Chapuis & Joel | publisher=IOS Press }}</ref>

By 1934, the London telephone area comprised all 147 exchanges within {{convert|12+1/2|mi|km|-1}} of [[Oxford Circus]].<ref name="charges">{{cite web | url=http://www.hartley-kent.org.uk/info/phone1.pdf | format=PDF | title=Reduced Charges | publisher=[[General Post Office]] | year=1934 | archive-url=https://web.archive.org/web/20131214152615/http://www.hartley-kent.org.uk/info/phone1.pdf | archive-date=14 December 2013 | url-status=live }}</ref> By 1950, the London Director system had 75 exchanges within a {{convert|5|mi|km|0|adj=on}} radius of Oxford Circus and a further 65 in the {{convert|5|-|10|mi|0|adj=on}} belt. In Greater London (in other words, within {{convert|20|mi|km}} of Oxford Circus), there were 237 exchanges.<ref>''Telephony: A detailed exposition of the telephone exchange system of the British Post Office'' by J Atkinson pp373,402 (1950 reprinted 1972, Pitman, London) {{ISBN|0 273 43181 1}}.</ref> In January 1956 a new director exchange – "SKYport" – was opened at [[London Heathrow Airport]].<ref name="flight">{{cite news | url=http://www.flightglobal.com/pdfarchive/view/1956/1956%20-%200176.html | title=Brevites | newspaper=Flight and Aircraft Engineer | date=6 January 1956 | archive-url=https://web.archive.org/web/20131212130926/http://www.flightglobal.com/pdfarchive/view/1956/1956%20-%200176.html | archive-date=12 December 2013 | url-status=live }}</ref>

===Exchange codes===
From 1922, the first three digits of a seven-digit subscriber number{{spaced ndash}}in other words, the local exchange codes{{spaced ndash}}were represented with letters by way of a [[mnemonic]]. Each three-character code corresponded to an exchange within the London telephone area. The subscriber numbers were written, for example, as "ABBey 1234" and "WIMbledon 1234" or "ABB 1234" and "WIM 1234". By 1965, there were 350 local exchanges in London and the number of permutations that could be used for exchange names had been exhausted.<ref name="Valdar 256-8">{{cite book | title=Understanding telecommunications networks | author=A R Valdar | publisher=Institution of Engineering and Technology | year=2008 | pages=256–8 }}</ref> With the change to [[all-figure dialling]] in 1966, the system of mnemonics was withdrawn and the three-digit local exchange codes of many subscribers were altered. The old codes continued to work in parallel with new codes until January 1970, when the "ANN: All-figure Numbers Now" advertising campaign prompted callers to use only the new codes.<ref name="connected">{{cite web | url=http://www.connected-earth.com/Journeys/Itpaystoadvertise/Thebirthofmarketing/Sellingthenetwork/ | title=Selling the network | publisher=Connected Earth | archive-url=https://web.archive.org/web/20131212223703/http://www.connected-earth.com/Journeys/Itpaystoadvertise/Thebirthofmarketing/Sellingthenetwork/ | archive-date=12 December 2013 | url-status=live }}</ref> The transition to all-figure dialling allowed the codes to be grouped into eight sectors; all exchanges within {{convert|6|km|mi}} of the centre of London formed the Central sector and the other sectors radiated from it.<ref name="Valdar 259">{{cite book | title=Understanding telecommunications networks | author=A R Valdar | publisher=Institution of Engineering and Technology | year=2008 | page=259 }}</ref>

{| class="wikitable"
! Sector
! Local exchange code prefixes
|-
| Central
| 21–28, 32, 35, 37, 38, 40, 43, 48, 49, 58, 60, 61, 62, 63, 70, 72, 73, 79, 82, 83, 92, 93
|-
| East
| 47, 50, 51, 52, 53, 55, 59, 98
|-
| South
| 64, 65, 66, 67, 68, 76, 77
|-
| South East
| 29, 30, 31, 46, 69, 85
|-
| South West
| 33, 39, 54, 78, 87, 94, 97
|-
| North
| 34, 36, 44, 80, 88
|-
| North West
| 20, 42, 45, 86, 90, 95, 96
|-
| West
| 56, 57, 74, 75, 84, 89, 99
|}

The first three digits of a subscriber number continued to indicate the exchange to which the number belonged; for example, "222 1234" was in Westminster (Central Sector) and "946 1234" in Wimbledon (South West Sector).<ref group="notes">The numerical codes for Westminster and Wimbledon did not change when all-figure dialling was introduced because the first two digits of their exchange codes corresponded to the sectors they became part of.</ref> More than one local exchange code was usually [[Overlay plan|overlaid]] for each area, so all Wimbledon numbers did not necessarily begin "946". Subscriber numbers changed to eight digits in 2000 when an additional 7 or 8 was added to each local exchange code (for example, "7222 1234" in Westminster and "8946 1234" in Wimbledon).

===STD code===
{| cellspacing=0 cellpadding=10 align="right" style="font-size:90%;margin-left:10px;border: 1px solid darkgray;"
! colspan="4" bgcolor=lightgray align="center" | Example telephone number
|-
| bgcolor=#ffffd0 align="center" | 1959–1966
| bgcolor=#ffffd0 align="center" | STD codes introduced
| bgcolor=#ffffd0 align="center" | 01-WIM 0123
|-
| bgcolor=#d0ffd0 align="center" | 1966–1990
| bgcolor=#d0ffd0 align="center" | [[All-figure dialling]]
| bgcolor=#d0ffd0 align="center" | 01-946 0123
|-
| bgcolor=#ffffd0 align="center" | 1990–1995
| bgcolor=#ffffd0 align="center" | Area code split
| bgcolor=#ffffd0 align="center" | 081-946 0123
|-
| bgcolor=#d0ffd0 align="center" | 1995–2000
| bgcolor=#d0ffd0 align="center" | [[PhONEday]]
| bgcolor=#d0ffd0 align="center" | 0181 946 0123
|-
| bgcolor=#ffffd0 align="center" | 2000–{{small|present}}
| bgcolor=#ffffd0 align="center" | [[Big Number Change]]
| bgcolor=#ffffd0 align="center" | 020 8946 0123
|}

The [[STD code]] 01 was assigned to the London telephone area on 6 April 1959 as part of preparations for [[subscriber trunk dialling]].<ref name="BT 1959">{{cite web | url=http://www.btplc.com/thegroup/btshistory/1912to1968/1959.htm | title=Events in Telecommunications History: 1959 | publisher=British Telecommunications PLC | archive-url=https://web.archive.org/web/20091014014724/http://www.btplc.com/Thegroup/BTsHistory/1912to1968/1959.htm | archive-date=14 October 2009 | url-status=live }}</ref> For the next thirty years, "01" became synonymous with the capital.<ref name="shows">For example, in the name of the cultural show ''[[01-for London]]'', broadcast by [[Thames Television]] between 1987 and 1990 ({{cite web | url=http://ftvdb.bfi.org.uk/sift/series/18117 | title=BFI Film & TV Database: 01-For London | access-date=25 September 2012 | archive-date=5 September 2011 | archive-url=https://web.archive.org/web/20110905071816/http://ftvdb.bfi.org.uk/sift/series/18117 | url-status=dead }}).</ref> Until May 1990, the 01 code covered the same area as the current 020 code and had capacity for fewer than 10 million telephone numbers.<ref name="Ofcom_new_code">{{cite web | url=http://stakeholders.ofcom.org.uk/binaries/telecoms/numbering/slides.pdf | format=PDF | author=Ofcom | author-link=Ofcom | publisher=Office of Communication | title=New Telephone Numbers for London | date=6 October 2004 | archive-url=https://web.archive.org/web/20110526041407/http://stakeholders.ofcom.org.uk/binaries/telecoms/numbering/slides.pdf | archive-date=26 May 2011 | url-status=live }}</ref>

In May 1990, the 01 code was abandoned and the area divided between 071{{spaced ndash}}which covered exchanges in the Central sector{{spaced ndash}}and 081, which covered all other sectors. Exceptionally, two exchanges in the East sector<ref group="notes">Albert Dock and Poplar exchanges were not in the Central sector but were included in the 071 code.</ref> covering the [[London Docklands]] redevelopment area were assigned the 071 code.<ref name="Split">{{cite web | url=http://www.samhallas.co.uk/repository/po_docs/london_code_change.pdf | format=PDF | title=How to use the new codes | publisher=British Telecom | archive-url=https://web.archive.org/web/20131213134732/http://www.samhallas.co.uk/repository/po_docs/london_code_change.pdf |archive-date=13 December 2013 | url-status=live }}</ref> The anticipation that the code associated with central districts would be more prestigious than the other associated with the outer suburbs<ref name="NY Times">{{cite news | url=https://www.nytimes.com/1990/05/06/world/london-will-divide-its-telephone-prefix-fraying-composure.html | title=London Will Divide Its Telephone Prefix, Fraying Composure | newspaper=The New York Times | date=6 May 1990 | archive-url=https://web.archive.org/web/20100828080501/http://www.nytimes.com/1990/05/06/world/london-will-divide-its-telephone-prefix-fraying-composure.html | archive-date=28 August 2010 | url-status=live }}</ref> was used as a plot device in the Essex-based TV comedy series ''[[Birds of a Feather (TV series)|Birds of a Feather]]''.<ref>{{cite episode | title=Brief Encounter | episode-link=Brief Encounter (Birds of a Feather) | series=Birds of a Feather | series-link=Birds of a Feather (TV series) | station=BBC One | date=18 October 1990 | series-no=2 | number=14 }}</ref> At the time of the split, there were five local exchange codes assigned to [[Mercury Communications]]<ref group="notes">Exchange codes 528, 895, 945, 975 and 982 were assigned to Mercury Communications.</ref> and numbers in these ranges could be assigned to either code.<ref name="Split"/> This area code split doubled the potential capacity.<ref name="Ofcom_new_code" /> In 1995, on "[[PhONEday]]", the codes changed again, to 0171 and 0181.

[[File:History of London STD codes.svg|frame|centre|Sequence of code changes.]]

The split into two area codes only lasted a decade. As part of the [[Big Number Change]] on 22 April 2000, the 0171 and 0181 codes were replaced with 020, following a period of dual-running that began on 1 June 1999 when the new 020 code was activated and ended on 14 October 2000 when the old 0171 and 0181 codes were finally ceased. The 22 April 2000 change also affected subscriber local numbers which gained an extra digit. "0171-xxx xxxx" numbers changed to "(020) 7xxx xxxx", while "0181-xxx xxxx" numbers became "(020) 8xxx xxxx". As a result of this history, there is now a [[UK telephone code misconceptions|widespread misconception]] that 0207 and 0208 are the dialling codes for parts of London.<ref name="ofcom_code">{{cite web | title=Telephone numbers – the facts and figures &#124; (Boxout) Is it (020) 7 or 0207? | url=http://www.ofcom.org.uk/consumer/2009/08/phone-numbers/#video | author=Ofcom | author-link=Ofcom | publisher=Office of Communication | archive-url=https://web.archive.org/web/20090830080116/http://www.ofcom.org.uk/consumer/2009/08/phone-numbers/#video#video | archive-date=30 August 2009 | url-status=dead | access-date=22 August 2009 | df=dmy-all }}</ref> This was exacerbated when local numbers beginning 3 started to be issued.

The reunification under a single code created capacity for approaching 100 million telephone numbers<ref name="Ofcom_new_code" /> and, starting in 2005, subscriber numbers beginning with the digit "3" were issued alongside those beginning "7" and "8".<ref name="Ofcom_new_code" /> In August 2019, Ofcom announced that subscriber numbers beginning with the digit "4" will also be introduced.<ref name="de Peyer">{{Cite news |url=https://www.standard.co.uk/news/london/capital-to-get-10m-new-landline-numbers-with-launch-of-new-dialling-code-a4225086.html |title=London to get 10million new landline numbers with launch of new dialling code  |last=de Peyer |first=Robin |date=30 August 2019 |work=[[Evening Standard]] |access-date=30 August 2019}}</ref>

===Charge group===
The London telephone area operated as a single group for charging purposes in which all calls were priced at local rate. Additionally, as was usual, calls to and from the adjacent charge groups were charged as local.<ref group="notes">Calls to London from each of the 01322, 01372, 01689, 01707, 01708, 01727, 01737, 01753, 01784, 01883, 01895, 01923, 01932, 01959 and 01992 area codes were charged at local rate, as were calls from London to each of those area codes.</ref>

==Coverage==
{{further|List of telephone exchanges in London}}
{{Location map+|Greater London
  |caption = Coverage of the 020 area code
  |float   = right
  |width   = 350
  |AlternativeMap = 020 UK dial code area - 2007.png
  |places  =
{{location map~|Greater London|mark=Blue_pog.svg|label=[[Central London]]|background=white|lat=51.5155|long=-0.0922|caption=|float=}}
{{location map~|Greater London|mark=Blue_pog.svg|label=[[Colindale]]|position=left|background = white|lat=51.5930|long=-0.2479|caption=|float=}}
{{location map~|Greater London|mark=Blue_pog.svg|label=[[Croydon]]|background = white|lat=51.3727|long=-0.1099|caption=|float=}}
{{location map~|Greater London|mark=Blue_pog.svg|label=[[Ealing]]|background = white|lat=51.5111|long=-0.3058|caption=|float=}}
{{location map~|Greater London|mark=Blue_pog.svg|label=[[Eltham]]|background = white|lat=51.4514|long=0.05177|caption=|float=}}
{{location map~|Greater London|mark=Blue_pog.svg|label=[[Kingston upon Thames|Kingston]]|background = white|lat=51.4103|long=-0.2995|caption=|float=}}
{{location map~|Greater London|mark=Blue_pog.svg|label=[[Ilford]]|background = white|lat=51.558807|long=0.085459|caption=|float=}}
{{location map~|Greater London|mark=Blue_pog.svg|label=[[Wood Green]]|background = white|lat=51.5981|long=-0.1149|caption=|float=}}
{{location map~|Greater London|mark=Black pog.svg|label=[[Romford]] (01708)|background = lightgray|position=right|lat=51.5798|long=0.189|caption=|float=}}
{{location map~|Greater London|mark=Black pog.svg|label=[[Uxbridge]] (01895)|background = lightgray|position=left|lat=51.5404|long=-0.4778|caption=|float=}}
{{location map~|Greater London|mark=Black pog.svg|label=[[Orpington]] (01689)|background = lightgray|position=bottom|lat=51.3741|long=0.0986|caption=|float=}}
{{location map~|Greater London|mark=|label={{nowrap|[[Bushey Heath]]}}|position=left|background = white|lat=51.637|long=-0.348|caption=|float=}}
{{location map~|Greater London|mark=|label=[[Elstree]]|background = white|lat=51.655|long=-0.278|caption=|float=}}
{{location map~|Greater London|mark=|label=[[Ewell]]|position=left|background = white|lat=51.351|long=-0.25|caption=|float=}}
{{location map~|Greater London|mark=|label=[[Loughton]]|background = white|lat=51.647|long=0.056|caption=|float=}}
{{location map~|Greater London|mark=|label={{nowrap|[[Thames Ditton]]}}|position=left|background = white|lat=51.383|long=-0.336|caption=|float=}}
}}
The code serves a roughly circular area with a radius of {{convert|20|km|mi}} from the centre of London. The Greater London boundary varies from {{convert|17|km|mi}} to {{convert|32|km|mi}} from the centre and consequently some outer districts are covered by adjacent codes and in some places the 020 code extends beyond the Greater London boundary. The code covers an area larger than the [[London postal district|London post town]] where letters addressed to "LONDON" are delivered.

The [[City of London]] and at least some part of all 32 [[London borough]]s are within the 020 area code. There are six exchanges outside Greater London that use the 020 code.<ref group="notes">Bushey Heath, Elstree, Ewell, Hainault (Chigwell), Loughton and Thames Ditton exchanges are outside Greater London.</ref> Communities outside Greater London that are within the code are [[Buckhurst Hill]], [[Chigwell]], [[Loughton]] and [[Sewardstone]] in Essex; [[Borehamwood]], [[Bushey]], [[Carpenders Park]], [[Elstree]] and [[South Oxhey]] in Hertfordshire; and [[Ewell]], [[Molesey]], [[Thames Ditton]] and [[Whyteleafe]] in Surrey.

There are eighteen exchanges within Greater London that do not use the 020 code.<ref group="notes">Biggin Hill, Crayford, Denham, Downland, Erith, Farnborough, Harefield, Hornchurch, Ingrebourne, Lodge Hill, Northwood, Orpington, Rainham, Romford, Ruislip, Slade Green, Upminster, Uxbridge and West Drayton do not use the 020 code.</ref> The six boroughs that have significant areas within other codes are [[London Borough of Bexley|Bexley]], partly within the Dartford (01322) code; [[London Borough of Bromley|Bromley]], partly within the Orpington (01689) and Westerham (01959) codes; [[London Borough of Croydon|Croydon]], partly within the Orpington (01689) and Redhill (01737) codes; [[London Borough of Enfield|Enfield]], partly within the Waltham Cross (01992) code; [[London Borough of Havering|Havering]], mostly within the Romford (01708) code; and [[London Borough of Hillingdon|Hillingdon]], partly within the Uxbridge (01895), Slough (01753) and Watford (01923) codes.
{{clear}}

==Number allocation==
With the introduction of the (020) area code, as part of the [[Big Number Change]], subscriber numbers were changed from 7-digits (xxx xxxx) to 8-digits (xxxx xxxx). This allowed new ranges of numbers to be issued. Under the [[National Telephone Numbering Plan]] the code operates with the following sub-ranges:

{| class="wikitable"
! colspan="2" | 020
|-
| 0xxx&nbsp;xxxx{{pad}}1xxx&nbsp;xxxx
| national dialling only
|-
| 2xxx&nbsp;xxxx
| reserved for future use
|-
| 3xxx&nbsp;xxxx
| new local numbers issued after move to 020 (since 2005)
|-
| 4xxx&nbsp;xxxx{{pad}}
| new local numbers issued after move to 020 (since 2019)
|-
| 5xxx&nbsp;xxxx{{pad}}6xxx&nbsp;xxxx
| reserved for future use
|-
| 70xx&nbsp;xxxx{{pad}}71xx&nbsp;xxxx
| new local numbers issued after move to 020 (since 2000)
|-
| 72xx&nbsp;xxxx{{pad}}73xx&nbsp;xxxx{{pad}}74xx&nbsp;xxxx{{pad}}75xx&nbsp;xxxx{{pad}} 76xx&nbsp;xxxx{{pad}}77xx&nbsp;xxxx{{pad}}78xx&nbsp;xxxx{{pad}}79xx&nbsp;xxxx{{pad}}
| local numbers transferred from 0171
|-
| 80xx&nbsp;xxxx{{pad}}81xx&nbsp;xxxx
| new local numbers issued after move to 020 (since 2000)
|-
| 82xx&nbsp;xxxx{{pad}}83xx&nbsp;xxxx{{pad}}84xx&nbsp;xxxx{{pad}}85xx&nbsp;xxxx{{pad}} 86xx&nbsp;xxxx{{pad}}87xx&nbsp;xxxx{{pad}}88xx&nbsp;xxxx{{pad}}89xx&nbsp;xxxx
| local numbers transferred from 0181
|-
| 9xxx&nbsp;xxxx
| reserved for future use
|}

In 2006 59% of numbers within the 020 code were allocated to [[BT Group|BT]].<ref name="hansard">{{cite hansard | title=Select Committee on London Local Authorities Bill Minutes of Evidence: Evidence Session (Sections 4400–4499) | url=https://publications.parliament.uk/pa/ld200506/ldselect/ldobclla0405/6032807.htm | house=House of Lords | date=28 March 2006 | archive-url=https://web.archive.org/web/20060422173544/http://www.publications.parliament.uk/pa/ld200506/ldselect/ldobclla0405/6032807.htm | archive-date=22 April 2006 | url-status=live }}</ref> The area code is not subject to number conservation and the regulator [[Ofcom]] does not restrict the size of number blocks that are allocated.<ref name="conservation">{{cite web | url=http://stakeholders.ofcom.org.uk/consultations/conserve/statement/ | title=Conserving geographic numbers | work=Statement | author=Ofcom | author-link=Ofcom | publisher=Office of Communication | date=8 April 2010 | archive-url=https://web.archive.org/web/20101111073908/http://stakeholders.ofcom.org.uk/consultations/conserve/statement/ | archive-date=11 November 2010 | url-status=live }}</ref>

==Notes==
{{Reflist|group=notes}}

==References==
{{Reflist}}

==External links==
* [https://web.archive.org/web/20140525024839/http://www.rhaworth.myby.co.uk/phreak/tenp_01.htm List of exchanges in 1966]
* [https://web.archive.org/web/20131215140426/http://tele.mar.cx/united_kingdom/20 Number allocations]

{{Telephone numbers in the United Kingdom}}

[[Category:Area codes in the United Kingdom|20]]
[[Category:Infrastructure in London]]