The Pimlico District Heating Undertaking is Britain's first district heating system. It was built in the 1950s and used heat from Battersea Power Station on the other side of the Thames. This picture shows the now disused heat and return pipes that go under the Thames, the first and only heat pipes under the Thames. Following the decommissioning of Battersea Power Station, the pipes are no longer in use. Engineers were once able to cross underneath the Thames using the tunnel but human access now requires breathing and survival gear.