Nathan Ellis from the Environment Agency explains how the Thames estuary barrier protects central London from storm waters.
Ten moveable gates guard against tides and keep London from a storm surge, which would add almost three and half metres to a tide - more than enough to flood central areas. It is one of the largest flood barriers in the world.
The barrier was engineered to defend against tide levels until 2030, though it is likely it will last long after that. The barrier is capable of withstanding a 1 in 1000 storm, which is predicted to hit in 2070.