By the late 19th century the need for another river crossing downstream from London Bridge was undeniable, despite vociferous opposition from ferrymen and other shipping interests. A census taken in August 1882 recorded more than 22,000 vehicles and 110,000 pedestrians crossing the 16m wide London Bridge in 24 hours. But downstream of London Bridge lay the Pool of London, one of the busiest ports in the world. A fixed crossing would have to provide much greater headroom than any other Thames bridge and be resistant to impact from much larger vessels.
Given the low banks along the tidal Thames, options for the designers were limited. On neither bank was there space for the long approach ramps that a fixed high level crossing would have required: the same restriction applied to the tunnel option. Other proposals included fixed high level crossings accessed by hydraulic elevators and a type of transporter bridge with the deck travelling on underwater rail lines. But the most obvious solution was some form of opening bridge. In 1878 City architect Horace Jones proposed a bascule bridge modelled on much smaller examples in Rotterdam and Copenhagen, and seven years later an Act of Parliament authorised its construction.
Named after the French word for see-saw, the advantage of the bascule bridge design over most alternatives is the minimum obstruction to shipping it presents in the open position. But the design finalised by engineer Sir John Wolfe Barry differs from all other bascule bridges in two key respects.
Visually, it predates Disneyland by many decades.
The mock Gothic architecture and Portland Stone cladding are non-structural decoration insisted on by the authorities in an attempt to blend the bridge with the adjacent Norman stonework of the Tower of London. Underneath is a classic Victorian steel, wrought iron and cast iron structure.
Conceptually it enshrines a major operational flaw. The bridge's designers anticipated that pedestrians would be unwilling to tolerate the delays occasioned by the frequent openings. So they provided, at vast expense, high level walkways accessed both by stairs and by 18 passenger hydraulic lifts, supported by 90m high towers.
This naturally limited the headroom under the bridge to a maximum of 43m at high tide, although the towers made the suspension side spans possible. As it turned out, the vast majority of pedestrians turned out to be quite happy to pause for the five or ten minutes the opening and closing sequence actually took, treating the passage of shipping as free entertainment.
Construction of the bridge officially began in April 1886 with the laying of the foundation stone by the Prince of Wales. The biggest challenge for the builders was the two main piers, which had to be constructed in a busy shipping channel using a system of small caissons. In all the project consumed 6,600m 3ofstone, 54,000m 3of concrete, 31M high strength engineering bricks and 14,000t of iron and steel. The total cost of the 800m long crossing was around £1M, and it opened on 30 June 1894.