The history of the Britannia Bridge, North Wales

The Britannia Bridge made use of Robert Stephenson’s iron tubular bridge design. 

When built it had the longest continuous wrought iron span in the world.

Devastated by fire in 1970, the bridge was rebuilt using the masonry supports in Stephenson’s original structure.

engineeering drawing of the Britannia Bridge

Watch a film all about the history of the Britannia Bridge (English and Welsh captions available.)

Linking Anglesey with the mainland

Proposed as a railway through North Wales, connecting London via Chester with the Port of Holyhead in Anglesey, the Chester and Holyhead Railway Act was passed in June 1845. Robert Stephenson was soon appointed its chief engineer.

By 1848 construction of the railway had been finished between Chester and Bangor and Llanfair PG and Holyhead. The bridge that would take the railway over the Menai Strait would make the line complete.

The bridge was to link the mainland just west of Bangor to the island of Anglesey, making use of the Britannia Rock midstream. As the Menai Strait was still a navigable channel towards the Irish Sea, the Admiralty stipulated that any bridge crossing it should pose no obstruction to shipping during construction, and must have headroom of 105ft (31.5m) above high water level.

Design and construction

Robert Stephenson proposed a tubular type of bridge; the railway line running through tubes made up of wrought iron riveted plates. The bridge consisted of two main spans of 460ft and two smaller spans at each side of 230ft, all supported by masonry towers, the tallest being the Britannia Tower at 221ft.

In this design, Stephenson was assisted by three men, William Fairburn (in designing the distinctive ‘tubes’ through which the trains originally ran), Eaton Hodgkinson (who investigated the strength of the tubular structure) and Edwin Clark (Stephenson’s resident engineer).

The two longest tubes were built in sections on the Caernarfon shore, and were floated into position using pontoons then raised onto the towers using a hydraulic jack. Once in position they were joined inside the tower making a continuous beam of 1511ft – at the time the longest wrought iron span in the world. On the wing walls at the end of each abutment tower, two grand lions, sculpted by John Thomas, kept watch. Both lines on the bridge were opened to traffic on 19 October 1850.

From the ashes of the old…

The Britannia Bridge remained unaltered, other than routine maintenance until a disastrous fire took hold in the tubes on 23 May 1970. Heat from the fire was so intense that the central tubes buckled and had to be dismantled. A new, open lattice steel arch bridge was designed by Husband & Co of Darlington which made use of Stephenson’s masonry towers.

The bridge reopened for rail traffic in 1972. By the mid 1970s as road traffic using the A5 over Thomas Telford’s road bridge across the Menai Straits was increasing, the decision was taken to transform the Britannia Bridge into a combined road and rail bridge. Construction of the road deck to the bridge started in October 1977 and opened to road traffic in 1980.

Did you know?

A memorial window to Robert Stephenson in Westminster Abbey contains a medallion depicting the Britannia Bridge. It can be found in the Abbey’s north choir aisle.

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