British hydrogen bomb programme

British hydrogen bomb programme
The Grapple 1 nuclear test on 15 May 1957. Hailed as Britain's first hydrogen bomb test, it was in fact a technological failure.
Type of project	Thermonuclear weapon deployment
Country	United Kingdom
Prime Minister(s)	Winston Churchill, Anthony Eden, Harold Macmillan
Key people	William Penney, William Cook
Established	1952
Disestablished	1958

The British hydrogen bomb programme was the ultimately successful British effort to develop hydrogen bombs between 1952 and 1958. During the early part of the Second World War, Britain had a nuclear weapons project, codenamed Tube Alloys. At the Quebec Conference in August 1943, British prime minister Winston Churchill and United States president Franklin Roosevelt signed the Quebec Agreement, merging Tube Alloys into the American Manhattan Project, in which many of Britain's top scientists participated. The British government trusted that America would share nuclear technology, which it considered to be a joint discovery, but the United States Atomic Energy Act of 1946 (also known as the McMahon Act) ended technical cooperation. Fearing a resurgence of American isolationism, and the loss of Britain's great power status, the British government resumed its own development effort, which was codenamed "High Explosive Research".

The successful nuclear test of a British atomic bomb in Operation Hurricane in October 1952 represented an extraordinary scientific and technological achievement. Britain became the world's third nuclear power, reaffirming the country's status as a great power, but hopes that the United States would be sufficiently impressed to restore the nuclear Special Relationship were soon dashed. In November 1952, the United States conducted 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 of the senior Cabinet members, considered the political and strategic implications in June 1954, and concluded that "we must maintain and strengthen our position as a world power so that Her Majesty's Government can exercise a powerful influence in the counsels of the world."^[1] In July 1954, Cabinet agreed to proceed with the development of thermonuclear weapons.

The scientists at the United Kingdom Atomic Energy Authority's Atomic Weapons Establishment at Aldermaston in Berkshire included William Penney, William Cook, Ken Allen, Samuel Curran, Henry Hulme, Bryan Taylor and John Ward. They did not know how to build a hydrogen bomb, but produced three designs: Orange Herald, a large boosted fission weapon; Green Bamboo, an interim thermonuclear design; and Green Granite, a true thermonuclear design. The first series of Operation Grapple tests involved Britain's first airdrop of a thermonuclear bomb. Although hailed as a success at the time, the first test of the Green Granite design was a failure. The second test validated Orange Herald as a usable design of a megaton weapon, but it was not a thermonuclear bomb, and the core boosting did not work. A third test attempted to correct the Green Granite design, but was another failure.

In the Grapple X test in November 1957, they successfully tested a thermonuclear design. The Grapple Y test the following April obtained most of its yield from nuclear fusion, and the Grapple Z test series later that year demonstrated a mastery of thermonuclear weapons technology. An international moratorium on nuclear tests commenced on 31 October 1958, and Britain ceased atmospheric testing for good. The successful development of the hydrogen bomb, along with the Sputnik crisis, resulted in the 1958 US–UK Mutual Defence Agreement, in which the nuclear Special Relationship was restored.