River Thames Thames Estuary), the river is subject to tidal activity from the North Sea. Before the lock was installed, the river was tidal as far as Staines, about upstream. London, capital of Roman Britain, was established on two hills, now known as Cornhill and Ludgate Hill. These provided a firm base for a trading centre at the lowest possible point on the Thames. A river crossing was built at the site of London Bridge. London Bridge is now used as the basis for published tide tables giving the times of high tide. High tide reaches Putney about 30 minutes later than
Tunnels underneath the River Thames such as the Queen Elizabeth II Bridge at Dartford. Tunnels underneath the River Thames The table below lists many of the tunnels under the River Thames in and near London, which, thanks largely to its underlying bed of clay, is one of the most tunnelled cities in the world. The tunnels are used for road vehicles, pedestrians, Tube and railway lines and utilities. Several tunnels are over a century old: the original Thames Tunnel was the world's first underwater tunnel. The figure and list above leave out at least three tunnels: under the Thames Barrier; the 2.8m diameter tunnel carrying