Following the success of Operation Grapple in which the United Kingdom became the third nation to acquire thermonuclear weapons after the United States and the Soviet Union, Britain launched negotiations with the US on a treaty under which both could share information and material to design, test and maintain their nuclear weapons. This effort culminated in the 1958 US–UK Mutual Defence Agreement. One of the results of that treaty was that Britain was allowed to use United States' Nevada Test Site for testing their designs and ideas, and received full support from the personnel there, in exchange for the data "take" from the experiment, a mutual condition. In effect the Nevada Test Site became Britain's test ground, subject only to advance planning and integrating their testing into that of the United States. This resulted in 24 underground tests at the Nevada Test Site from 1958 through the end of nuclear testing in the US in September 1992.
The United Kingdom signed the Comprehensive Nuclear Test Ban Treaty in 1996 and ratified it in 1998, confirming the British commitment towards ending nuclear test explosions in the world.
Background
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, the Prime Minister, Winston Churchill and the President of the United States, Franklin Roosevelt, signed the Quebec Agreement, which merged Tube Alloys with the American Manhattan Project to create a combined British, American and Canadian project. The British government had trusted that the United States would continue to share nuclear technology, which it regarded as a joint discovery, but the United States Atomic Energy Act of 1946 (McMahon Act) ended technical cooperation. The British government feared that there might be a resurgence of United States isolationism, as had occurred after the First World War, in which case Britain might have to fight an aggressor alone, and that Britain might lose its great power status and its influence in world affairs. It therefore restarted its own development effort, now codenamed High Explosive Research.
Implicit in the decision to develop atomic bombs was the need to test them. Lacking open, thinly-populated areas, British officials considered locations overseas. The preferred site was the American Pacific Proving Grounds. A request to use it was sent to the American Joint Chiefs of Staff, but no reply was received until October 1950, when the Americans turned down the request. The uninhabited Monte Bello Islands in Australia were selected as an alternative. Meanwhile, negotiations continued with the Americans. Oliver Franks, the British Ambassador to the United States, lodged a formal request on 2 August 1951 for use of the Nevada Test Site. This was looked upon favourably by the United States Secretary of State, Dean Acheson, and the chairman of the United States Atomic Energy Commission (AEC), Gordon Dean, but opposed by the Robert A. Lovett, the Deputy Secretary of Defense and Robert LeBaron, the Deputy Secretary of Defence for Atomic Energy Affairs. In view of security concerns, Lovett and LeBaron wanted the tests to be conducted by Americans, with British participation limited to selected British scientists. President Harry S. Truman endorsed this counterproposal on 24 September 1951.
The Nevada Test Site would be cheaper than Monte Bello, although the cost would be paid in scarce dollars. Information gathered would have to be shared with the Americans, who would not share their own data. It would not be possible to test from a ship, and the political advantages in demonstrating that Britain could develop and test nuclear weapons without American assistance would be foregone, and the Americans were under no obligation to make the test site available for subsequent tests. Also, as Lord Cherwell noted, an American test meant that "in the lamentable event of the bomb failing to detonate, we should look very foolish indeed." In the end, Monte Bello was chosen, and the first British atomic bomb was tested there in Operation Hurricane on 3 October 1952. The next British test series, Operation Totem, was conducted at Emu Field in South Australia, but at their conclusion, the British government formally requested a permanent testing site from the Australian government, which led to the agreement on the use of the Maralinga test site in August 1954. The first of the British nuclear tests at Maralinga was held in September 1956.
While British atomic bomb development represented an extraordinary scientific and technological achievement, hopes that the United States would be sufficiently impressed to restore the nuclear Special Relationship were dashed. In November 1952, the United States conducted Ivy Mike, 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, 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." In July 1954, Cabinet agreed to proceed with the development of thermonuclear weapons.
The Australian government would not permit thermonuclear tests in Australia, so Christmas Island in the Pacific was chosen for Operation Grapple, the testing of Britain's thermonuclear designs. The Grapple tests were facilitated by the United States, which also claimed the island. Although the initial tests were unsuccessful, the Grapple X test on 8 November 1957 achieved the desired result, and Britain became only the third nation to develop thermonuclear weapon technology. The British weapon makers had demonstrated all of the technologies that were needed to produce a megaton hydrogen bomb that weighed no more than and was immune to premature detonation caused by nearby nuclear explosions. A one-year international moratorium commenced on 31 October 1958, and Britain never resumed atmospheric testing.
The Soviet Union's launch of Sputnik 1 on 4 October 1957, came as a tremendous shock to the American public, and amid the widespread calls for action in response to the Sputnik crisis, officials in the United States and Britain seized an opportunity to mend the Anglo-American relationship that had been damaged by the Suez Crisis the year before. The Prime Minister, Harold Macmillan, wrote to President Dwight D. Eisenhower on 10 October, urging that the two countries pool their resources, as Macmillan put it, to meet the Soviet challenge on every front, "military, economic and political."
The McMahon Act was amended to allow limited exchanges of nuclear weapons data and non-nuclear components of nuclear weapons to nations that had made substantial progress in the field. Only Britain qualified as a nation that had made substantial progress. The bill was signed into law by Eisenhower on 2 July 1958, and the 1958 US–UK Mutual Defence Agreement (MDA) was signed by Dulles and Samuel Hood, the British Minister in Washington, the following day, and approved by the United States Congress on 30 July, thus restoring the Special Relationship. Macmillan called it "the Great Prize".
Testing The MDA did not specifically address British nuclear testing at the Nevada Test Site (NTS), but it did provide a high-level framework for it to occur. The prospect was raised by the British Ambassador to the United States, Sir Roger Makins, at a meeting with the Chairman of the AEC, Glenn T. Seaborg, and Sir William Penney, the head of nuclear weapons development at the United Kingdom Atomic Energy Authority (UKAEA). On 3 November 1961, Macmillan wrote to President John F. Kennedy requesting the use of the Nevada Test Site for the testing of Super Octopus, a British kiloton warhead intended for use with the American Skybolt missile that was of great interest to weapon designers on both sides of the Atlantic. The response was positive, and on 8 February 1962, Seaborg announced, specifically referencing the MDA, that there would be a UK nuclear test at the NTS. This developed into a procedure for approval of a British nuclear test. The director of the British Atomic Weapons Research Establishment (AWRE) would lodge a request with the chairman of the AEC, who would then make a recommendation to the president through the Secretary of State and the Secretary of Defence. Every test had to be approved by the president and the National Security Council.
A Joint Working Group (JOWOG) was set up to coordinate the British tests. Test safety and containment requirements remained a US Federal responsibility. The JOWOG therefore decided that the UK would provide the test device and diagnostics package, while the US would provide everything else, including the test canister and the data cables leading from it to the trailers with US recording equipment. This threw up issues regarding the interface between the British diagnostics package and the American recording equipment. There were also issues related to procedures, particularly with regard to the testing of electronic and mechanical devices. A further complicating factor was that the US had two rival nuclear weapons laboratories, the Los Alamos National Laboratory (LANL) and the Lawrence Livermore National Laboratory (LLNL), with different procedures.
For the first test, E. R. Drake Seager from the AWRE was designated the trial superintendent and Robert Campbell from LANL was designated the test director, these being the styles of the heads of the British and American teams. The test, codenamed Pampas, was conducted on 1 March 1962. It was Britain's first underground test. The new Super Octopus implosion system worked but the overall result was disappointing. The RO.106 (Tony) warhead was based on the American Tsetse warhead, but used a different, safer but less powerful conventional explosive, EDC11. The result was that the yield was less than Tsetse, and too small to be used as the primary in the Skybolt warhead. A follow-up test of what became the basis for the WE.177 design codenamed Tendrac therefore took place on 7 December 1962, and was judged a success.
Subcritical tests were tests with nuclear weapons that did not involve a nuclear explosion. Safety tests involved testing the impact of fire, shock and other accidents against live nuclear weapons. These did not intentionally involve nuclear explosions, although there was always a danger. Tim subcritical tests and Vixen safety tests related to WE.177 were conducted at Maralinga in March and April 1963, but four more British safety tests were conducted in 1963 at the NTS Tonopah Test Range as part of Operation Roller Coaster: Double Tracks on 15 May, Clean Slate 1 on 25 May, Clean Slate 2 on 31 May and Clean Slate 3 on 9 June. The Partial Nuclear Test Ban Treaty, which went into effect on 10 October 1963, banned atmospheric nuclear testing, and the Maralinga range was closed for good in 1967.