Railway Bridge

Railway bridge, 1836–8 with 1878–82 and 20th-century extensions; designed by Isambard Kingdom Brunel.

The bridge consists of two semi-elliptical arches built in London stock brick with white hydraulic mortar, matching brick string courses, and dressed gritstone copings. The southern span (1836–8) is 30 feet and retains its original southern abutment and approach with gently-splayed flanking abutments. The northern span (1878–82), measuring 25 feet, has steeply-angled wing walls. There is no buttress to the central pier. The parapets show evidence of 19th-century and 20th-century rebuilding, with recent reconstructions of terminal pilasters and the north-west and south-east corners.

Originally constructed as a standard London stock brick overbridge 13 feet 6 inches wide for unclassified lanes, the bridge accommodated two broad-gauge tracks (subsequently two mixed broad- and standard-gauge tracks from 1861 until the abolition of broad gauge in 1892). During the Slough–Maidenhead quadrupling of 1878–82, the northern abutment was largely demolished and the structure extended to the north with a matching arched span.

The bridge was erected as part of Isambard Kingdom Brunel's contracts 4L and 5L between spring 1836 and May 1838, when the Paddington–Maidenhead line opened. It formed part of the main London to Bristol line of the Great Western Railway, constructed between 1835 and 1841. Brunel, appointed company engineer of the Bristol Railway (later the Great Western Railway) in 1832 at age 26, oversaw a comprehensive and distinctive design philosophy: careful route surveying and gentle gradients, adoption of the 7-foot 0¼-inch broad gauge for stability at speed, and a combination of showpiece engineering structures and more prosaic bridges and viaducts.

The Leigh Road bridge retains more of its original 1836–8 fabric than many surviving Brunel bridges on the London to Maidenhead section, making it an excellent exemplar of the broad-gauge concept despite later extensions.