1958 US–UK Mutual Defence Agreement as an atomic spy, caused the proposal to be dropped. The June 1951 defection of Donald Maclean, who had served as a British member of the Combined Policy Committee from January 1947 to August 1948, reinforced the Americans' distrust of British security arrangements. The first British atomic bomb was successfully tested in Operation Hurricane on 3 October 1952, but although it was more advanced than the American bombs of 1946, Britain was still several years behind in nuclear weapons technology. The United States conducted Ivy Mike, the first nuclear test of a true thermonuclear device (also known as a hydrogen
Referendums in the United Kingdom "alien device". As of 2018, only three national referendums have ever been held across the whole of the United Kingdom: in 1975, 2011 and most recently in 2016. Two of these referendums were held on the issue of the United Kingdom's relationship with Europe with the first held on the issue of continued membership of what was known at the time as the European Communities (EC), which was the collective term for the European Coal and Steel Community (ECSC), the European Economic Community (EEC) and the European Atomic Energy Community (EAEC), and was also referred to by many at that