Britain Goes Nuclear
Britain was the first country to investigate the development of nuclear weapons. Work by Otto Frisch and Rudolf Peierls in Febuary 1940, and the MAUD Committee (a code name chosen from the first name of one member's nanny) report showed the feasibility of fission weapons. British scientists, known as "the British Mission," later made major contributions to the Manhattan Project.
However, with the 1946 passing of the Atomic Energy Act, also known as "The McMahon Act," ties between U.S. and British nuclear programs were severed. As the Cold War began, Great Britain felt it should have an independent nuclear force. In January 1947, plans were formed to develop a British nuclear weapon.
Led by Sir John Crockcroft, Britain's first nuclear reactor went critical on July 3, 1948. Sites for plutonium production and highly enriched uranium were also constructed.
Due to the small size, no suitable sites for atmospheric weapons tests existed. Britain thus sought sites in other countries to test its weapons, finally settling on the Monte Bello Islands, off the west coast of Australia. On October 3, 1952, Britain detonated its first atomic device, code-named "Hurricane." It had an explosive yield of about 25 kilotons.
In 1954, Churchill decided that Britain should go ahead with hydrogen bomb development. Britain's first successful hydrogen bomb was detonated on November 8, 1957, over Christmas Island in the Pacific. The test had a yield of 1.8 megatons.
Following an amendment to the Atomic Energy Act in 1958, cooperation between U.S. and British nuclear programs resumed. After the 1957-'58 test series, the United Kingdom ceased conducting its own independent nuclear tests. Once nuclear testing resumed in 1961, the U.S. and Britain also began conducting joint tests at the Nevada Test Site. All subsequent British nuclear weapons were based on U.S. designs, which were made available to Britain.