THE THAMES BARRIER Reports of the capital being flooded date back to the Anglo Saxon Chronicle of 1099. The great floods of 1236 were so severe that people could row boats inside Westminster Hall. The idea of a barrier was prompted by severe floods in 1953 which claimed the lives of over 300 people and drenched 160,000 acres of farmland in salt water. Charles Draper's innovative design which uses radial gates on sills developed from the gas tap principle was commissioned in 1965 and by 1982, the capital was prepared to withstand the onslaught of a surge tide - a great hump of water travelling at between 50 and 60 miles an hour along the Thames estuary. The Thames Barrier is an impressive feat of engineering and continues to be the world's largest moveable flood barrier, spanning one third of a mile across the river at Woolwich Reach. The structure is protected from cracking with specially designed SKS Sliding Bearings. These are located between structural elements to control the small movements resulting from loading, thermal or seasonal changes. The bearings accommodate anticipated movements (typically +/- 10mm but sometimes +/- 25mm or greater) whilst ensuring that the load is transmitted evenly (eg through the centre of a supporting wall rather than along its edge).