The BT Tower is a communications tower located in Fitzrovia, London, owned by BT Group. It has been previously known as the Post Office Tower, Thames TV Tower, the London Telecom Tower and the British Telecom Tower. The main structure is 581 feet high, with a further section of aerial rigging bringing the total height to 627 ft. Upon completion it overtook the Millbank Tower to become the tallest building in both London and the United Kingdom, titles it held until 1980, when it was overtaken by the NatWest Tower. The tower was topped out on 15 July 1964 and officially opened by the then Prime Minister Harold Wilson on 8 October 1965.