Laid like an iron necklace across the Thames, as of May this year, the Thames Barrier has protected central London from flooding 119 times since it went operational in 1982. The barrier spans 520 metres of the river near Woolwich, east of the City, and is one of the largest moveable flood barriers in the world. It features 10 steel gates, each of which weighs 3,000 tonnes, which can be raised or lowered. They stand as high as a five-storey building when up and, while you may not think they look it, the piers, which are covered with a protective ‘skin’ of stainless steel, are wide enough apart to accommodate the largest of ships. There are regular boat trips to the barrier from central London and there is an information centre about the barriers which includes a cafe (boats don’t stop at the Thames Barrier Pier, so this can’t be accessed from the river itself). For more on the barrier and the information centre, see www.environment-agency.gov.uk/homeandleisure/floods/38353.aspx.