Digswell Viaduct

Digswell Viaduct
A photo of a landscape as viewed from a drone shot. It is a sunset in a valley with a arched railway viaduct cutting through the image. The viaduct has metal masts at periodic points and the bottom of the arches are partially covered in the photo by trees.
The viaduct as viewed by drone
Coordinates51°49′07″N 0°11′41″W / 51.8186°N 0.1947°W / 51.8186; -0.1947
CarriesEast Coast Main Line
CrossesRiver Mimram
Official nameWelwyn Railway Viaduct
Other nameWelwyn Viaduct
Heritage statusGrade II* listed
Characteristics
Total length1,450 feet (440 m)
Height100 feet (30 m)
No. of spans40
Rail characteristics
No. of tracks2
Electrified25kV AC OHLE
History
DesignerWilliam Cubitt
Joseph Cubitt
Constructed byThomas Brassey
Opened7 August 1850
Location
Interactive map of Digswell Viaduct

The Digswell Viaduct, also known as the Welwyn Viaduct and officially the Welwyn Railway Viaduct, is a railway viaduct that carries two tracks of the East Coast Main Line over the Mimram Valley in Hertfordshire in the East of England. A prominent local landmark, it is located between Welwyn Garden City and Welwyn North railway stations, and is located above the village of Digswell and the River Mimram. Designed by father and son William and Joseph Cubitt, and engineered by Thomas Brassey, the viaduct opened in 1850 and has been a Grade II* listed structure since 1980.

The viaduct has forty arches and was originally built from red facing bricks, with blue facing bricks added in the 1930s. Metal gantries were appended to the side of the viaduct in 1980 as part of the electrification of the Great Northern route. At approximately 1,560 feet (475 m) in length, and around 100 ft (30 m) in height, it was one of the largest works on the Great Northern Railway when it opened.

Design

The viaduct carries two tracks of the East Coast Main Line across the River Mimram and its valley. The viaduct was styled to be similar to Roman aqueducts, and was one of the largest works on the GNR when it was built. It has forty arches, and is built from thirteen million red bricks, which were fired using clay that had been mined during the construction of the viaduct. The records of Earl Cowper, who owned the land, gave the precise number of bricks produced on the site as 13,975,638, but some of these would have been used to build Welwyn North station and line the Welwyn Tunnels. Each pier was built with 65 piles driven into the ground by means of a steam-fuelled piling engine. The viaduct is the first perfectly level section of the ECML out of King's Cross.

The waterproofing originally consisted of a 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. These systems were replaced in 1986. Due to the nature of the ground in the Mimram Valley, eleven of the forty piers were reinforced with timber, for which 19,844 cubic feet (561.9 m3) was needed. The viaduct joins embankments at both ends, which used approximately one million tons of earth to build; this was all moved by manpower and horsepower.

The viaduct has become a prominent part of local history in Welwyn and has been Grade II* listed since 4 November 1980, meaning that it is a "particularly important [structure] of more than special interest". Historic England's 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". According to an official document by East Herts District Council It has sometimes been referred to by locals as one of the "seven wonders of Hertfordshire".

Dimensions

The height and length of the viaduct are not recorded consistently. The National Heritage List for England (NHLE) entry for the viaduct, citing The Railway Heritage of Britain, gives its length as 519 yards (475 m), which is the same as the figure in Welwyn & Welwyn Garden City in 50 Buildings. The original plans suggested the viaduct would be 521 yards (476 m), and British Railways' concurred with this length when asked by the authors of Welwyn's Railways, who, having seen various figures, settled on "about 520 yards (480 m)", which is the figure in Eastern and Central England volume of Civil Engineering Heritage, in Wrottesley's The Great Northern Railway, and in an official document published by East Herts District Council. Charles H. Grinling's The History of the Great Northern Railway, 1845–1922 suggests the completely different length of 497 yards (454 m). This figure and 520 yards are suggested in Rook's River Mimram. There is no disagreement between sources in the length of a span at 30 ft (9 m).

The height of the viaduct increased as a result of electrification. The pre-electrification figure given in Wrottesley's The Great Northern Railway is a maximum of 89 feet (27 m) above the ground. Welwyn's Railways and Civil Engineering Heritage suggest that since electrification its maximum height is 98 feet (30 m), whereas its NHLE entry and Welwyn & Welwyn Garden City in 50 Buildings give the figure as 100 feet (30 m). An official document published by East Herts District Council refers to the height as "nearly 100 feet (30 m)". Rook's River Mimram quotes "almost 100 feet (30 m)" but also 110 feet (34 m) as possible heights.

A photograph of an arched brick railway viaduct as taken from the ground quite some distance away. The whole viaduct is in the shot but some is obscured by trees and shrubbery. A red and white express train is passing over the viaduct beneath the metal masts attached to the arches.
The viaduct as viewed from Digswell Park Road in 2020

History

1848–1850: Construction and opening

The viaduct, as illustrated in The Illustrated London News, 10 August 1850

The viaduct was built for the Great Northern Railway (GNR) between 1848 and 1850, in order to carry their line between King's Cross and Welwyn (now Welwyn North), although they planned for this to extend to York. The contract had begun in 1846, and bricks were made from 1847. It is the largest viaduct on the GNR's main line. The viaduct was designed by railway engineers William Cubitt, the GNR's chief engineer, and his son Joseph Cubitt. Some sources attribute it to Lewis Cubitt, who was of no close relation to William and Joseph.

The railway engineer George Hudson opposed the viaduct's construction, saying that it 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. In order to support the viaduct, a 2,200,000-cubic-yard (1,700,000 m3) trench was excavated and then packed with clay and mortar. Due to the inconsistent ground in the valley, eleven of the piers also had to have timber added to their structure. The construction of the viaduct came at a cost of £69,397, which was equivalent to £8,077,000 in 2025. This was a cost per mile of 133.20, ten times more expensive than the rest of the line. The project was carried out by Thomas Brassey, who stayed in the Cowpers Arms while his workmen lived in temporary huts in Digswell. The workers had recently returned from a project in France, and their behaviour led to complaints from locals, who began to call them the 'tray bong' gang because of their use of French phrases.

The viaduct was opened along with the rest of the line between London and Peterborough on 7 August 1850. The inaugural trip left at 9:00, and involved 400 people travelling from Maiden Lane to Peterborough to view the newly-built line. The train stopped at Welwyn to allow people to disembark and view the viaduct. However, there exists an urban legend that Queen Victoria opened the viaduct a day earlier on 6 August. The legend says that when her train reached the viaduct, she refused to travel on the train across it because she was scared of its height above the valley. Instead, she was purported to have left the train to cross the viaduct without her and wait at Welwyn, while she travelled across the valley on the ground by horse-drawn cart. While Queen Victoria was not in fact present at the opening of the viaduct, she did use it in 1851 when travelling to Balmoral. On this journey, which was in receipt of significant press coverage at the time, she crossed the viaduct without issue and no sources suggest that she objected to doing so.

1851–present: Operation and refurbishment

Part of a railway viaduct as viewed at an angle from up close on the ground. The brick arches of the viaduct are incredibly tall and there are periodic metal masts attached to the top, with some trees on the flat grassy ground.
The viaduct in 2009, showing a closer view of the added electrification gantries.

In 1858, the tie rods were strengthened to further support the viaduct, because cracks in the brickwork had been noted. At the time, laden goods trains had also been crossing at 40 miles per hour (64 km/h), so a restriction of 15 mph (24 km/h) was implemented. 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.

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 shunted at the time. The 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, which is equivalent to £55,000 in 2025.

By the 1930s, a layer of salt had begun to appear on the red facing bricks on the viaduct, and they were considered too weak to prevent against further weathering. To solve this problem, an extra layer of 9.1-inch (230 mm) blue facing bricks were also added to the viaduct in a project that was completed in October 1935. Overall, 1.18 million bricks were required to complete the project, at a cost of £25,000, equivalent to £1,500,000 in 2025. Tie bars were then added to reinforce both layers of bricks in 1965. As part of the electrification of the Great Northern route by British Rail in the 1970s, overhead lines were added to the viaduct with metal gantries suspended on both sides in Autumn 1974. Extra drainage and waterproofing work was completed on the viaduct in 1986. This work had started in 1984, but were delayed by theft. A waterproof trackbed cover was also added during the same works.

Capacity issues

The Welwyn bottleneck includes Welwyn North railway station (foreground), the Digswell Viaduct (overhead gantries visible), and ends at Digswell Junction heading south (background)

The viaduct only carries two tracks, causing a bottleneck as the railway narrows from four tracks, which is the limiting factor for capacity on the congested and strategically important route. This problem is exacerbated by Welwyn North railway station being situated at the northern end of the viaduct, which blocks the line while trains are stationary, and by two tunnels to the north. Various ideas to overcome the limitations of the viaduct and station without damaging the viaduct's essential historic character and rhythmic design are periodically discussed.

Capacity issues have been raised since as early as the 1890s, when the Hertford Loop line was extended to Stevenage in order to prevent having to widen the viaduct from two tracks to four. The project was completed in 1898, 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. The cost of extending the Hertford Loop line was £1.25 million (equivalent to £144,000,000 in 2025), which was considered more expensive than quadrupling the bottlenecks at Potters Bar and Welwyn but came with the benefit of increased passenger usage from the newly served stations. The Department for Transport's 2006 study on railway capacity raised the issue again. A 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. To coincide with this, Welwyn railway station was renamed to Welwyn North. This arrangement is still the case today.

In August 2013, BBC News listed the idea of widening the viaduct and the adjacent Welwyn Tunnels to four tracks 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". As of 2015 Network Rail set the maximum capacity of the bottleneck at 18 trains per hour (tph). The East Coast Main Line 2016 Capacity Review considered the quadrupling of the viaduct and Welwyn North railway station, concluding it would not fully resolve the capacity constraints", only increasing capacity for intercity trains by 2–3tph. 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.

See also

Notes

  1. 1 2 3 4 To the nearest 10 feet (3.0 m); see § Dimensions
  2. ↑ I.e. an eye dialect transcription of très bon

References

  1. 1 2 "London North Eastern Sectional Appendix" (PDF). National Electronic Sectional Appendix. Network Rail. pp. 206–208. 7 June 2025. Retrieved 23 June 2025.
  2. 1 2 3 4 5 6 7 8 9 10 11 Rutherford, Cameron (17 July 2022). "The Hertfordshire viaduct that frightened Queen Victoria". HertsLive. Archived from the original on 22 June 2025. Retrieved 22 June 2025.
  3. 1 2 3 4 5 Humber, William, ed. (1865). A Record of the Progress of Modern Engineering. London: Lockwood & Company. pp. 31–32. OCLC 181795100. Archived from the original on 23 June 2025. Retrieved 23 June 2025.
  4. ↑ Jowett, Alan (1989). Jowett's Railway Atlas. Patrick Stephens Ltd. p. 119A. ISBN 978-1852600860.
  5. 1 2 3 4 "APPENDIX 2: Issues in defining and measuring railway capacity" (PDF). Office of Rail Regulation. 13 February 2006. p. 2. Archived from the original on 6 April 2025. Retrieved 28 February 2014.
  6. 1 2 3 4 5 6 7 8 9 10 11 12 Historic England. "Welwyn Railway Viaduct (1348122)". National Heritage List for England. Retrieved 22 June 2024.
  7. ↑ "Welwyn Hatfield District Plan 2005 Appendix 2: Listed Buildings". Welwyn Hatfield. 2005. Archived from the original on 4 March 2016. Retrieved 2 February 2014.
  8. 1 2 3 4 5 6 Wallace, Eileen (2010). Children of the Labouring Poor: The Working Lives of Children in Nineteenth-century Hertfordshire. University of Hertfordshire Press. pp. 121–122. ISBN 978-1905313495. Archived from the original on 23 June 2025. Retrieved 23 June 2025.
  9. 1 2 3 4 5 6 Rabbitts, Paul; Jeffree, Peter (2021). "27. Digswell Viaduct". Welwyn & Welwyn Garden City in 50 Buildings. Amberley Publishing Limited. ISBN 978-1398102484. Archived from the original on 23 June 2025. Retrieved 23 June 2025.
  10. 1 2 3 4 5 Labrum, E. A. (1998). Eastern and Central England. Civil Engineering Heritage. Thomas Telford. ISBN 978-0-7277-1970-6.
  11. 1 2 Biddle, Gordon (2011). Britain's Historic Railway Buildings: A Gazetteer of Structures (second ed.). Hersham: Ian Allan. p. 121. ISBN 9780711034914.
  12. 1 2 3 4 5 6 Rook, Tony (2014). "7: Digswell Viaduct and Digswell Water". River Mimram. Amberley Publishing. ISBN 978-1-4456-3328-2.
  13. ↑ Gladwin, Neville & White 1986, p. 13,15.
  14. 1 2 Sowden, Maurice (2020). "20.5 Case History: Waterproofing the Welwyn Viaduct". Maintenance of Brick and Stone Masonry Structures. CRC Press. ISBN 978-1000143867.
  15. ↑ "What Are Listed Buildings?". Historic England. 11 February 2025. Archived from the original on 18 June 2025. Retrieved 22 June 2025.
  16. 1 2 3 4 "Landscape Character Assessment" (PDF). East Herts District Council. September 2007. p. 53.
  17. 1 2 3 4 5 6 7 Gladwin, Neville & White 1986, p. 35.
  18. 1 2 3 Wrottesley, John (1979). The Great Northern Railway. Vol. I: Origins and Development. B. T. Batsford. p. 52. ISBN 0-7134-1590-8.
  19. 1 2 Historic England. "Welwyn North Railway Station and Footbridge (1385391)". National Heritage List for England. Retrieved 23 June 2025.
  20. ↑ Labrum, E. A. (1998). Eastern and Central England. Civil Engineering Heritage. Thomas Telford. ISBN 978-0-7277-1970-6.
  21. ↑ Pevsner, Nikolaus; Cherry, Bridget (2002). Hertfordshire. Yale University Press. p. 224. ISBN 978-0300096118. Archived from the original on 25 September 2025. Retrieved 25 September 2025.
  22. ↑ NHerts. "Building Welwyn Viaduct charcoal drawing; Samuel Lucas senior; 1850; 2912". eHive. Archived from the original on 25 September 2025. Retrieved 25 September 2025.
  23. ↑ "The Cubitts". Camden Railway Heritage Trust. Archived from the original on 13 July 2025. Retrieved 28 September 2025.
  24. ↑ "Sir William Cubitt". London Remembers. Archived from the original on 8 August 2025. Retrieved 28 September 2025.
  25. ↑ Gladwin, Neville & White 1986, p. 36–37.
  26. 1 2 3 4 UK Consumer Price Index inflation figures from 1209–2024 based on data from "Inflation calculator". Bank of England. London. 18 February 2026. Retrieved 1 April 2026.
  27. 1 2 3 4 5 6 Gladwin, Neville & White 1986, p. 37.
  28. ↑ Gladwin, Neville & White 1986, p. 37–38.
  29. ↑ Acworth, William Mitchell (1889). The Railways of England (3rd ed.). London: J. Murray. p. 244. Archived from the original on 23 June 2025. Retrieved 23 June 2025.
  30. ↑ "Railway Law of the Week". The Railway News & Joint Stock Journal. 3 (62): 220. 4 March 1865 – via Google Books.
  31. ↑ British Railways Board. "Your New Electric Railway: The Great Northern Suburban Electrification" (PDF). Archived (PDF) from the original on 24 September 2015. Retrieved 15 April 2010.
  32. ↑ "Bypassing the Welwyn bottleneck : Elizabeth line to the ECML". RailEnable. 8 March 2021. Archived from the original on 20 July 2023. Retrieved 20 July 2023.
  33. ↑ Phillips, Charles (6 March 2025). The Great Eastern Railway - From the Grouping to the Elizabeth Line 1923–2023. Pen and Sword Transport. pp. 20–21. ISBN 978-1036103606. Archived from the original on 10 May 2025. Retrieved 23 June 2025.
  34. ↑ Nick de Bois (28 January 2014). "First Capital Connect (Hertford Loop)". Parliamentary Debates (Hansard). Vol. 574. Parliament of the United Kingdom: Westminster Hall. col. 225WH–227WH. Archived 18 June 2025 at the Wayback Machine
  35. ↑ Gladwin, Neville & White 1986, p. 14.
  36. ↑ Butt, R. V. J. (October 1995). The Directory of Railway Stations: details every public and private passenger station, halt, platform and stopping place, past and present (1st ed.). Sparkford: Patrick Stephens Ltd. p. 244. ISBN 978-1-85260-508-7. OCLC 60251199. OL 11956311M.
  37. ↑ Catford, Nick (26 May 2017). "Welwyn Garden City Halt". Disused Stations. Archived from the original on 24 January 2025. Retrieved 8 December 2024.
  38. ↑ "Could these five projects improve life in the UK?". BBC News. 13 August 2013. Retrieved 22 June 2025.
  39. ↑ "Is there a solution to the East Coast conundrum?". RailReview. 30 June 2025. Retrieved 29 March 2026.
  40. ↑ Review of Strategic Alternatives to High Speed Two (PDF) (Report). Network Rail. November 2011. p. 32. Retrieved 29 March 2026.
  41. ↑ "Concern as land by Digswell Viaduct goes up for auction tomorrow". Welwyn Hatfield Times. 22 June 2020. Archived from the original on 22 June 2025. Retrieved 22 June 2025.

Sources

51°49′07″N 0°11′41″W / 51.8186°N 0.1947°W / 51.8186; -0.1947