The Her Majesty's Naval Base Clyde lies on the western coast of Scotland, 40 km (25 mi) west of Glasgow in the Faslane area. A nuclear submarine fleet is based at the site, facilitated by Prime Minister Clement Attlee's authorisation of a British nuclear weapons programme in 1947. A 1958 agreement between the UK and the United States (US) was followed by a 1962 US agreement, whereby it provided information about its submarine-launched missile system, "Polaris". The UK's first Polaris submarine, HMS Resolution, was launched in 1968 and the entire system was modified in the early 1970s to the British "Chevaline" system.