The Thames Barrier is located downstream of central London, United Kingdom. Operational since 1982, its purpose is to prevent the floodplain of all but the easternmost boroughs of Greater London from being flooded by exceptionally high tides and storm surges moving up from the North Sea..
The barrier was officially opened on 8 May 1984 by Queen Elizabeth II. Total construction cost was around £534 million (£1.3 billion at 2001 prices) with an additional £100 million for river defences. Built across a 520-metre (570 yd) wide stretch of the river, the barrier divides the river into four 61-metre (200 ft) and two, approximately 30 metre (100 ft) navigable spans. It will be celebrating 30 years anniversary on 8 May 2014.