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
Leslie H. Martin off the coast of Western Australia in October 1952, and then for Operation Totem tests at Emu Field in South Australia in October 1953. When the British government established the Maralinga Test Range in 1953, the Australian government created the Maralinga Safety Committee, which became the Atomic Weapons Test Safety Committee, with Martin as its chairman. As such he was responsible for safety of the Operation Mosaic tests at Monte Bello in May and June 1956, and Operation Buffalo tests at Maralinga in September and October 1956, after which he handed over the chairmanship to Ernest Titterton. An advocate for