The Alexandra Palace television station in North London (grid reference TQ297901) is one of the oldest television transmission sites in the world. What was at the time called "high definition" (405-line) TV broadcasts on VHF were beamed from this mast from 1936 until the outbreak of World War II. It then lay dormant until it was used very successfully to foil the German Y-Gerät radio navigation system during the last stages of the Battle of Britain. After the war, it was reused for television until 1956, when it was superseded by the opening of the BBC's new main transmitting station for the London area at Crystal Palace.