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
British nuclear testing in the United States which led to the agreement on the use of the Maralinga test site in August 1954. The first of the British nuclear tests at Maralinga was held in September 1956. While British atomic bomb development represented an extraordinary scientific and technological achievement, hopes that the United States would be sufficiently impressed to restore the nuclear Special Relationship were dashed. In November 1952, the United States conducted Ivy Mike, the first successful test of a true thermonuclear device or hydrogen bomb. Britain was therefore still several years behind in nuclear weapons technology. The Defence Policy Committee, chaired by Churchill and consisting