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 . On 1 November , the United States conducted Ivy Mike , the first nuclear test of a true thermonuclear device ( also known as a hydrogen bomb ) . The JCAE saw little benefit for the United States from sharing technology with Britain . The Soviet Union responded with the test of Joe 4 , a boosted fission weapon on 12 August 1953 . This prompted President Dwight Eisenhower , who was inaugurated in January 1953 , to inform the United States Congress that the McMahon Act , which he considered a " terrible piece of legislation " and " one of the most deplorable incidents in American history of which he personally felt ashamed " , was obsolete
Ivy Mike
Ivy Mike
1958 US–UK Mutual Defence Agreement