The Thames Barrier is the largest movable flood barrier in the world, 520 metres wide, and it was built to protect Central London from flooding caused by surge tides coming up the river. Severe flooding in 1953 caused a huge amount of damage along the east coast and the loss of over 300 lives, and serious consideration was then given to the construction of a barrier across the Thames which together with the strengthening of defences downstream would prevent flooding all along the river. 

The closure of the docks and demise of large shipping in the Thames meant that less consideration had to be given to navigational needs, and Woolwich Reach became a feasible site. Openings of only 200 feet could be used, the same width as Tower Bridge, and the barrier could therefore be constructed nearer to London than originally envisaged. The barrier was designed by Rendel, Palmer and Tritton, one of Britain’s oldest and most highly regarded firms of consulting engineers, for the Greater London Council, begun in 1974 and completed in 1982. It was officially opened by the Queen on 8 May 1984. The barrier is formed by ten steel rising sector gates supported by concrete piers housing the operating machinery. The six gates across the main navigation openings in the centre of the river are normally out of sight, lying flat on the river bed resting on concrete sills. They have a D-shaped section and rotate up into the raised position, when they rest against the sills to form a seal. The engineer responsible for this concept was Charles Draper, using the principle of a gas tap. The piers have hood-like silver tops like halves of upturned boats, constructed from wood and clad with stainless steel, which form the distinctive view of the barrier that is normally seen. On the south side is the control building and beneath it is a covered walkway beside the riverSince it was built, the barrier has been raised as a protective measure over 39 times. Items used in the construction of the barrier have been preserved, painted and made into sculptures. On the east side of the Control Tower, on a grass bank, are two funnels known as tremies (GR 125) used to pour concrete into the foundations of the piers, and on the west side are an anchor and chain which were used for mooring the concrete sill units