In 1952 , the United Kingdom became the third nation to possess nuclear weapons when it detonated an atomic bomb in Operation Hurricane on October 3 , 1952 , which had a yield of 25 kilotons . Despite major contributions to the Manhattan Project by both Canadian and British governments , the U.S. Congress passed the Atomic Energy Act of 1946 , which prohibited multi-national cooperation on nuclear projects . The McMahon Act fueled resentment from British scientists and Winston Churchill , as they believed that there were agreements regarding post-war sharing of nuclear technology , and led to Britain developing its own nuclear weapons . Britain did not begin planning the development of their own nuclear weapon until January 1947 . Because of Britain ’s small size , they decided to test their bomb on the Monte Bello Islands , off the coast of Australia . Following this successful test , under the leadership of Churchill , Britain decided to develop and test a hydrogen bomb . The first successful hydrogen bomb test occurred on November 8 , 1957 , which had a yield of 1.8 megatons . An amendment to the Atomic Energy Act in 1958 allowed nuclear cooperation once again , and British-U.S. nuclear programs resumed . During the Cold War , British nuclear deterrence came from submarines and nuclear-armed aircraft . The Resolution class ballistic missile submarines armed with the American-built Polaris missile provided the sea deterrent , while aircraft such as the Avro Vulcan , SEPECAT Jaguar , Panavia Tornado and several other Royal Air Force strike aircraft carrying WE .177 gravity bomb provided the air deterrent
Operation Hurricane
Operation Hurricane
Nuclear arms race