View source for Digswell Viaduct

{{Short description|Railway viaduct in the East of England}}
{{Use dmy dates|date=February 2018}}
{{Use British English|date=February 2018}}

{{Infobox bridge
| name = Digswell Viaduct
| image = Digswell Viaduct at sunset - filmed by drone.jpg
| caption = The viaduct as viewed by drone
| carries = [[East Coast Main Line]]
| crosses = [[River Mimram]]
| official_name = Welwyn Railway Viaduct
| other_name = Welwyn Viaduct
| height = 100 ft (30 m)
| number_spans = 40
| notrack = 2
| electrification = 25kV AC OHLE<ref name="NESA206-208">{{NESA|region=LNE|page=206–208|access-date=23 June 2025}}</ref>
| designer = [[William Cubitt]]<br>
[[Joseph Cubitt]]
| builder = [[Thomas Brassey]]
| open = 7 August 1850
| opened = 
| mapframe = yes
}}

The '''Digswell Viaduct''',<ref name=":0" /><ref name=":1">{{Cite book |url=https://www.google.co.uk/books/edition/A_Record_of_the_Progress_of_Modern_Engin/EsVlMeEGHYMC?hl=en&gbpv=0 |title=A Record of the Progress of Modern Engineering |date=1865 |publisher=Lockwood & Company |editor-last=Humber |editor-first=William |editor-link=William Humber |location=London |pages=31–32 |language=en-GB}}</ref> also known as the '''Welwyn Viaduct'''<ref>{{Cite book |last=Jowett |first=Alan |title=Jowett's Railway Atlas |publisher=Patrick Stephens Ltd. |year=1989 |isbn=978-1852600860 |page=119A}}</ref><ref name=":2" /> and officially the '''Welwyn Railway Viaduct''',<ref name="NHLE">{{NHLE|num=1348122|desc=WELWYN RAILWAY VIADUCT|access-date=22 June 2024}}</ref><ref>{{cite web |date=2005 |title=Welwyn Hatfield District Plan 2005 Appendix 2: Listed Buildings |url=http://welhat.leadpartners.co.uk/document.aspx?appendix=2 |url-status=dead |archive-url=https://web.archive.org/web/20160304035210/http://welhat.leadpartners.co.uk/document.aspx?appendix=2 |archive-date=4 March 2016 |access-date=2 February 2014 |publisher=[[Welwyn Hatfield]]}}</ref> is a railway viaduct that carries the two tracks of the [[East Coast Main Line]] over the Mimram Valley in the [[East of England|East of England.]] A prominent local landmark, it is located between [[Welwyn Garden City railway station|Welwyn Garden City]] and [[Welwyn North railway station|Welwyn North]] railway stations, and is located above the village of [[Digswell]] and the [[River Mimram]]. It has been [[Grade II* listed]] since 1980.

The viaduct has forty arches and was originally built from red facing bricks, with blue facing bricks also added in the 1930s. Metal gantries were added to the side of the viaduct in 1980 as part of the electrification of the [[Great Northern route]]. At {{convert|1560|ft|m|0}} in length and up to {{convert|100|ft|m|0|abbr=on}} in height, it was the one of the largest works on the Great Northern Railway when it opened in 1850.

== Design ==
The viaduct carries the [[East Coast Main Line]] across the Mimram Valley.<ref name=":2" /><ref name=":3">{{Cite book |last=Wallace |first=Eileen |url=https://www.google.co.uk/books/edition/Children_of_the_Labouring_Poor/0RaCcx3U_IAC?hl=en&gbpv=0 |title=Children of the Labouring Poor: The Working Lives of Children in Nineteenth-century Hertfordshire |date=2010 |publisher=Univ of Hertfordshire Press |isbn=978-1-905313-49-5 |pages=121–122 |language=en-GB}}</ref> Due to the width of the viaduct, the railway narrows from four tracks to two tracks, making it a [[traffic bottleneck|bottleneck]] which is the limiting factor for capacity on the congested and strategically important route.<ref name=":2">{{cite web |date=13 February 2006 |title=APPENDIX 2: Issues in defining and measuring railway capacity |url=http://orr.gov.uk/__data/assets/pdf_file/0018/5751/its_uleeds_app2.pdf |access-date=28 February 2014 |publisher=[[Office of Rail Regulation]] |page=2}}</ref> This problem is exacerbated by [[Welwyn North railway station]] situated at the northern end of the viaduct, which blocks the line while trains are stationary, and by two tunnels to the north. Several ideas to overcome the limitations of the viaduct and station without damaging the viaduct's essential historic character and rhythmic design are periodically discussed.<ref>{{cite web |date=8 March 2021 |title=Bypassing the Welwyn bottleneck : Elizabeth line to the ECML |url=https://railenable.com/crossrail/crossrailecml.php |website=RailEnable}}</ref>

The viaduct was styled to be similar to [[Roman aqueduct|roman aqueducts]],<ref name=":0">{{Cite web |last=Rutherford |first=Cameron |date=2022-07-17 |title=The Hertfordshire viaduct that frightened Queen Victoria |url=https://www.hertfordshiremercury.co.uk/news/history/queen-victoria-frightened-digswell-viaduct-7316548 |access-date=2025-06-22 |website=Herts Live |language=en}}</ref> and was one of the largest works on the [[Great Northern Railway (Great Britain)|Great Northern Railway]] when it was constructed.<ref name=":1" /> It is around {{convert|1560|ft|m|0}} in length and comprises forty arches with a maximum height of {{convert|100|ft|m|0|abbr=on}}. It is built from red brick, and the entire viaduct took thirteen million of these bricks to build,<ref name="NHLE" /><ref name=":4">{{Cite book |last=Rabbitts |first=Paul |url=https://www.google.co.uk/books/edition/Welwyn_Welwyn_Garden_City_in_50_Building/evtZEAAAQBAJ?hl=en&gbpv=0 |title=Welwyn & Welwyn Garden City in 50 Buildings |last2=Jeffree |first2=Peter |date= |publisher=Amberley Publishing Limited |year=2021 |isbn=978-1-3981-0248-4 |language=en |chapter=27. Digswell Viaduct}}</ref> which were fired from clay mined from the same site at the time the viaduct was being built.<ref name=":0" /> Each pier was built with 65 [[Piling|piles]] driven into the ground by steam-fuelled piling engine.<ref name=":1" />

The original waterproofing originally consisted of a [[Bitumen|bitumen membrane]], which the brickwork was covered with so that the water would drain into cast iron pipes at the centre of each pier. The drainage system had become clogged over time but this could not be fixed as the pipes were inaccessibly positioned inside the viaduct. Furthermore, the membrane's efficacy had deteriorated to a point that water was leaking through and running down inside the brickwork.<ref name=":5">{{Cite book |last=Sowden |first=Maurice |url=https://www.google.co.uk/books/edition/Maintenance_of_Brick_and_Stone_Masonry_S/mMHyDwAAQBAJ?hl=en&gbpv=0 |title=Maintenance of Brick and Stone Masonry Structures |date= |publisher=CRC Press |year=2020 |isbn=978-1-000-14386-7 |language=en |chapter=20.5 Case History: Waterproofing the Welwyn Viaduct}}</ref> These systems were subsequently replaced in 1986.<ref name=":0" />

Due to the nature of the ground in the Mimram Valley, eleven of the forty piers were reinforced with [[timber]], for which {{Convert|19844|cuft|m3}} was needed.<ref name=":1" /> The viaduct joins embankments at both ends, which used approximated one million tons of earth to build; this was all moved by manpower and horsepower.<ref name=":0" /> The construction of the viaduct has been described as a "great engineering feat" and the viaduct has become a prominent part of local history in Welwyn.<ref name=":0" /><ref name=":3" />

The viaduct has been [[Grade II* listed]] since 4 November 1980,<ref name="NHLE" /> meaning that it is a "particularly important [structure] of special interest".<ref>{{Cite web |date=2025-02-11 |title=What Are Listed Buildings? {{!}} Historic England |url=https://historicengland.org.uk/listing/what-is-designation/listed-buildings/ |access-date=2025-06-22 |website=historicengland.org.uk |language=en}}</ref> [[Historic England|Historic England's]] official list description for the viaduct describes it as "An impressively monumental and elegant railway viaduct of 40 arches for the Great Northern Railway by eminent engineers Sir William and Joseph Cubitt".<ref name="NHLE" />

{{Wide image|Welwyn Railway Viaduct 2020-06-13.jpg|900px|The viaduct as viewed from Digswell Park Road in 2021}}

== History ==

=== 1848–1850: Construction and opening ===
The viaduct was built for the [[Great Northern Railway (Great Britain)|Great Northern Railway]] between 1848–1850,<ref name="NHLE" /><ref name=":4" /> and was built to carry their line between [[London King's Cross railway station|Kings Cross]] and [[Welwyn North railway station|Welwyn]] (now Welwyn North), although they planned for this to extend to [[York railway station|York]].<ref name=":3" /><ref name=":6">{{NHLE|num=1385391|desc=WELWYN NORTH RAILWAY STATION AND FOOTBRIDGE|access-date=23 June 2025}}</ref> The viaduct was designed by railway engineers [[William Cubitt]],<ref name="NHLE" /> who at the time was the Chief Engineer of the Great Northern Railway,<ref name=":1" /> and his son [[Joseph Cubitt]]. Prominent railway engineer [[George Hudson]] opposed the viaduct's construction, saying that the viaduct would collapse into the valley due to the nature of the ground, but also because he wanted to protect his monopoly on the [[Midlands]]' railways.<ref name=":3" />
[[File:Digswell_Viaduct_1864.png|thumb|The Digswell Viaduct in October 1864]]
The construction of the viaduct came at a cost of £69,397,<ref name="NHLE" /> which is equivalent to £{{Inflation|index=UK|value=69397|start_year=1850|r=-3|fmt=c}} in {{Inflation/year|index=UK}}.{{Inflation/fn|index=UK}} The construction of the viaduct was delivered by [[Thomas Brassey]],<ref name="NHLE" /> who stayed in the Cowpers Arms while his workmen lived in temporary huts in [[Digswell]]. The behaviour of these workmen led to complaints from locals, and they became known locally as the 'tray bong' (i.e. an anglicised ''très bon'') gang from their poor French.<ref name=":3" />

There is an urban myth that the viaduct was officially opened by [[Queen Victoria]] on 6 August 1850, but she was reportedly so frightened of its height that she refused to travel across it and left the train, using a horse-drawn carriage to travel the length of the bridge on the ground. However, this is unlikely because her diaries show that she was staying at [[Osborne House]] on the Isle of Wight on that day.<ref name=":0" /> 

The actual opening of the line, including the viaduct, was on 7 August 1850.<ref name="NHLE" /> The inaugural trip left at 9:00, and involved 400 people travelling from Kings Cross to Peterborough to view the newly-built line. The train stopped at Welwyn to allow people to disembark and "view the magnificent viaduct by which the railway there crossed the valley". Although Queen Victoria was not present at this opening, she did use the viaduct in 1851 to travel to Balmoral, and her journey received significant press coverage at the time; there is no record of her refusing to cross the viaduct during this journey.<ref name=":4" />

=== 1851–present: operation and refurbishment ===
On 7 October 1864, a [[Midland Railway]] train collided with a freight train belonging to the Great Northern Railway on the viaduct, which was being [[Shunting (rail)|shunted]] at the time. The [[Points (rail)|points]] were set incorrectly such that the train was shunted onto the main line rather than the sidings, where the collision then occurred. The Great Northern Railway immediately took responsibility for the accident, however a court case, ''Drakeford vs. the Great Northern'', arose as to the [[damages]] owed to the Midland Railway. A jury eventually settled these damages at £500,<ref>{{Cite journal |date=4 March 1865 |year=1865 |title=Railway Law of the Week |url=https://www.google.co.uk/books/edition/Railway_News_Finance_and_Joint_stock_Com/d3wqAQAAIAAJ?hl=en&gbpv=0 |journal=The Railway News & Joint Stock Journal |volume=3 |issue=62 |page=220 |via=[[Google Books]]}}</ref> which is equivalent to £{{Inflation|index=UK|value=500|start_year=1864|r=-3|fmt=c}} in {{Inflation/year|index=UK}}.{{Inflation/fn|index=UK}}
[[File:Digswell or Welwyn Viaduct - geograph.org.uk - 1557494.jpg|thumb|The viaduct in 2009, showing a closer view of the added electrification gantries.]]
In 1858, the [[Tie rod|tie rods]] were strengthened to further support the viaduct.<ref name=":0" /> In response to signs of deterioration appearing by the 1930s, an extra layer of {{Convert|9.1|in|mm}} blue facing bricks were also added to the viaduct in a project that was completed in 1935.<ref name=":0" /><ref name=":5" /> Tie bars were then added to reinforce both layers of bricks in 1965.<ref name=":0" /> As part of the electrification of the [[Great Northern route]] by [[British Rail]] in the 1970s,<ref name="GNS">
{{cite web |author=British Railways Board |author-link=British Railways Board |title=Your New Electric Railway: The Great Northern Suburban Electrification |url=http://www.railwaysarchive.co.uk/documents/BRE_GNElectric1973.pdf |access-date=15 April 2010}}
</ref> overhead lines were added to the viaduct with metal gantries suspended on the side.<ref name="NHLE" /> Extra drainage and waterproofing work was completed on the viaduct in 1986.<ref name=":0" />

In his 1889 book ''The Railways of England,'' [[William Mitchell Acworth]] reports that the Great Northern Railway traditionally considered the viaduct to be more important than the roof of Kings Cross, and yet somehow "not perfectly safe". According to Acworth, the company's engineers used to get regular letters and telegrams from worried passengers about its safety; however, engineers never found any issues with the structure.<ref>{{Cite book |last=Acworth |first=William Mitchell |url=https://www.google.co.uk/books/edition/The_Railways_of_England/E53tAAAAMAAJ?hl=en&gbpv=0 |title=The Railways of England |date=1889 |publisher=J. Murray |edition=3rd |publication-place=London |pages=244 |language=en}}</ref>

Capacity issues have been raised since as early as the 1890s, when the [[Hertford Loop line]] was extended to [[Stevenage railway station|Stevenage]] in order to prevent having to widen the viaduct from two tracks to four. The project was completed in 1898,<ref>{{Cite book |last=Phillips |first=Charles |url=https://www.google.co.uk/books/edition/The_Great_Eastern_Railway_From_the_Group/l4JDEQAAQBAJ?hl=en&gbpv=0 |title=The Great Eastern Railway - From the Grouping to the Elizabeth Line 1923-2023 |date=2025-03-06 |publisher=Pen and Sword Transport |isbn=978-1-0361-0360-6 |pages=20–21 |language=en}}</ref> and the Hertford Loop line is still used as a diversionary route for trains today when there is disruption on the East Coast Main Line.<ref>{{Cite Hansard|title=First Capital Connect (Hertford Loop)|jurisdiction=Parliament of the United Kingdom|house=Westminster Hall|date=28 January 2014|volume=574|url=https://hansard.parliament.uk/commons/2014-01-28/debates/14012862000001/FirstCapitalConnect(HertfordLoop)|column_start=225WH|column_end=227WH|speaker=[[Nick de Bois]]}}</ref> Capacity issues were raised again in the [[Department for Transport]]'s 2006 study on railway capacity.<ref name=":2" />

A [[Welwyn Garden City railway station|new station]] opened in the new town of [[Welwyn Garden City]] in September 1926, replacing the halt that had been built shortly after the town was incorporated in 1920.<ref name="Butt">{{harvnb|Butt|1995|p=244}}</ref><ref name="Disused Stations">{{cite web |last=Catford |first=Nick |date=26 May 2017 |title=Welwyn Garden City Halt |url=http://www.disused-stations.org.uk/w/welwyn_garden_city_halt/index.shtml |access-date=8 December 2024 |website=Disused Stations}}</ref> To coincide with this, Welwyn railway station was renamed to Welwyn North.<ref name=":6" /> This arrangement is still the case today.<ref name="NESA206-208" />

In August 2013, [[BBC News]] listed the quadrupling of the viaduct and adjacent Welwyn Tunnels as one of the top five infrastructure projects that could improve life for people in the United Kingdom. It estimated the cost of such a project at £440 million and considered its likelihood to be "probable, at some point".<ref>{{Cite news |date=2013-08-13 |title=Could these five projects improve life in the UK? |url=https://www.bbc.com/news/magazine-23587557 |access-date=2025-06-22 |work=BBC News |language=en-GB}}</ref> In June 2020, locals raised concerns at proposals to build developments on land adjacent to the railway that was used to graze animals. Locals requested that [[Welwyn Hatfield Borough Council]] restrict development in the area due to its value to the landscape of the Mimram Valley.<ref>{{Cite web |date=2020-06-22 |title=Concern as land by Digswell Viaduct goes up for auction tomorrow |url=https://www.whtimes.co.uk/news/22382591.concern-land-digswell-viaduct-goes-auction-tomorrow/ |access-date=2025-06-22 |website=Welwyn Hatfield Times |language=en}}</ref>

== See also ==

* [[Ouse Valley Viaduct]] on the Brighton Main Line
* [[Ribblehead Viaduct]] on the Settle–Carlisle line
* [[Glenfinnan Viaduct]] on the West Highland Line

== References ==
{{Reflist}}

==External links==
{{Commons category|Welwyn Viaduct}}
*{{Cite AV media |url=https://www.youtube.com/watch?v=xdqMx2J8rXg&ab_channel=CasperAerialVideos |title=Flying Scotsman at Digswell Viaduct |date=19 June 2021 |type=Video |publisher=Casper Aerial Videos |via=[[YouTube]]}}
*{{Cite AV media |url=https://www.youtube.com/watch?v=2e9xGOcj9ZI&ab_channel=DronefootageUK |title=Digswell Viaduct welwyn by Drone footage uk |date=10 February 2023 |type=video |publisher=Drone footage UK |via=[[YouTube]]}}

{{Listed buildings in Hertfordshire}}
[[Category:Railway viaducts in Hertfordshire]]
[[Category:Buildings and structures in Welwyn Hatfield (district)]]
[[Category:Grade II* listed buildings in Hertfordshire]]
[[Category:East Coast Main Line]]
[[Category:Grade II* listed bridges in England]]
{{Great Northern Route}}

{{Coord|51|49|06|N|0|11|41|W|region:GB|display=title}}