For years, London's East End was denied a new bridge because of the need to guarantee passage of ships up and down the Thames. For years, the greatest engineers of the age hunted for a design that would keep both road and water traffic moving. As Rob Bell explains, the solution came from architect Horace Jones, whose revolutionary design, with its thousand-tonne opening sections, was powered by nothing more than water. Rob also explains the bridge was lucky to survive the Second World War, having been a target for German V-1 flying bombs.