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
Radar, Anti-Aircraft No. 3 Mk. 7 ten years off suggested no major production should take place, as developments in the interim would render any radars built in that period obsolete. However, various events in 1949, notably the first Soviet atomic test, led to sweeping upgrades, including the first contract for production Mk. 7's. These began to arrive in 1952. The Swiss Air Force received twelve Mk. 7's in 1958, which they referred to as Feuerleitradar ("fire control radar") Mark VII. They combined them with their own predictor, the Hasler-built "Kommandogerät" ("command device") 43/50R. Like its British counterpart, the 43/50R could be fed information directly from the