While Isambard Kingdom Brunel’s pioneering Wharncliffe Viaduct was under construction in the early stages of building the Great Western Railway from 1836, he was simultaneously engaged on a more audacious project, the Maidenhead Viaduct, where the line needed to cross the River Thames.
The Thames Navigation Commissioners were adamant that the river channel and both towpaths must not be obstructed, yet Brunel was determined to restrict the ruling gradient of the railway to 1 in 1,320 (0.076%).
He located the crossing to take advantage of a midstream island, Bucks Ait, that could accommodate a bridge pier, and designed two brickwork spans, each 128 feet long, that rose only 24 feet in height. The arches remain the flattest brick spans ever constructed.
The GWR directors lacked Brunel’s confidence in his design, especially after the contractor, William Chadwick, lowered the centring before the mortar had fully set, and the lower courses of the eastern arch dropped half an inch.
Chadwick took responsibility and reinstated the brickwork, but Brunel was ordered to leave the centring in place when trains began to cross the bridge in July 1839.
His response was to quietly lower the timberwork a few inches, so that arches were self-supporting, while insisting that they remain in situ over the coming winter. Brunel’s biographer, L T C Rolt, wryly observes, “The suspicion that this was due not so much to excessive caution as to an impish sense of humour is hard to resist.”
Indeed, when an autumn storm destroyed the centring and the bridge remained firm, Brunel’s critics were silenced.
The artist J M W Turner depicted the Maidenhead Viaduct in his painting ‘Rain, Steam and Speed’ (1844), the first time a railway train had been portrayed in a sophisticated work of art.
The Maidenhead Viaduct remains almost exactly as it was built, except that it was widened in 1877 by Sir John Fowler, who took great trouble to preserve the proportions of Brunel’s design, though he used darker Cattybrook brick from Gloucestershire. When the broad-gauge tracks were removed in 1892 the line was quadrupled.
Similar care to preserve the beauty of Brunel’s engineering was taken when the line was electrified in 2017.
Oddly, when the viaduct was listed in 1950 only the western arch was designated Grade II*; the eastern arch was added to the designation in 1985. The entire bridge was upgraded to Grade I in 2012.
The name “The Sounding Arch” arose because of the spectacular echo. If you stand underneath the arch on the Taplow towpath and clap, you may be rewarded with six or more echoes. People on TripAdvisor complain that there isn’t an echo. People complaining on TripAdvisor is not uncommon.