Britain’s south-eastern coastline is low-lying, and faces relatively shallow waters. This makes London naturally vulnerable to the surges created when high tides coincide with North Sea storms, and shove water back up the Thames. We have records of the city being flooded since the Anglo-Saxon era. In 1236 there were boats rowing through the Palace of Westminster; in 1928 the Tate Gallery was drenched in mud. After a surge in 1953 killed hundreds of people across the Thames Estuary, the government commissioned a report on what to do from the mathematician and cosmologist Hermann Bondi. The result was the Thames Barrier at Woolwich, operational since 1983.