The United States and the United Kingdom have long enjoyed a “special relationship” of close partnership, so it seemed natural that the two nations should work together to develop an atomic weapon. Nevertheless, the story of U.S.-U.K. nuclear partnership is one of both collaboration and division. Although British scientists played a crucial role in the success of the Manhattan Project, a desire for secrecy and security prevented permanent nuclear collaboration until 1958. The British atomic bomb was thus both an offshoot of the American program and an independent project.

Early Years

The United Kingdom was in many ways the birthplace of atomic imagination and scientific research. One of the first steps toward the development of atomic energy was the research of Ernest Rutherford, a New Zealand-born British physicist and recipient of the 1908 Nobel Prize in Chemistry. In 1917, Rutherford became the first person to split the atom, leading to further speculation about the existence and structure of the neutron. Neutrons would be discovered by Rutherford’s colleague and former student James Chadwick in 1932. Rutherford’s work would influence other nuclear physicists. Many of them would go on to work on the British atomic project and the Manhattan Project, including Chadwick, Niels Bohr, and Mark Oliphant.

Caption: Ernest Rutherford in his laboratory

In addition to the early research successes of its scientists, British literary and political rhetoric also propagated speculation of a “super weapon” long before the atomic bomb was ever proved possible. In his 1914 novel, The World Set Free, British author H.G. Wells described atomic energy as “a source of power so potent that a man might carry in his hand the energy to light a city for a year, fight a fleet of battleships, or drive one of our giant liners across the Atlantic.” While fictionalization of the atomic bomb did not contribute directly to its development, the aura surrounding atomic energy in Britain certainly fueled the growing interest in nuclear physics.

Fiction was not the only source of atomic imagination to come out of Britain. Years before he became Prime Minister, Winston Churchill was fascinated by the idea of an atomic bomb. In a 1931 speech entitled “Fifty Years Hence,” Churchill asserted, “High authorities tell us that new sources of power, vastly more important than any we yet know, will surely be discovered. Nuclear energy is incomparably greater than the molecular energy which we use today… There is no question among scientists that this gigantic source of energy exists” (Farmelo 4). Less than a decade later, the discovery of nuclear fission by Otto Hahn and Fritz Strassmann would start the race for the bomb.

Preliminary Organization

The outbreak of World War II was a catalyst for the development of the atomic bomb. Alarmed by Hitler’s mention of a “secret weapon,” the British government began taking the bomb project much more seriously. Mark Oliphant reorganized research at Birmingham University, where he would bring together Otto Frisch and Rudolf Peierls. Together, the two physicists calculated that an atomic bomb could in fact be built and wrote their findings in a memorandum, “On the Construction of a ‘Super-Bomb’” (Farmelo 142).

Caption: Birmingham University

In May 1940, Winston Churchill became Prime Minister. In direct response to the Frisch-Peierls memorandum, one of his first acts was the creation of a uranium subcommittee to advise his government on how to proceed. It would eventually be known as the MAUD Committee, an inconspicuous name actually referring to the former caretaker of the Bohrs’ children. When the Germans invaded Denmark, Bohr had asked that news of his safety be sent to Frisch and to “Maud Ray Kent.” The confused scientists at first thought the message contained coded instructions. They later realized that it in fact referred to a person, Maud Ray, who lived in Kent.

The MAUD Committee proceeded in absolute secrecy. They were not allowed to recruit anyone the government classified as an “illegal alien,” including Frisch and Peierls. They also excluded Hans Halban and Lew Kowarski, who had come to England after the fall of France together with the entire world’s supply of heavy water at the time. The two would go on to conduct vital experiments independent of the MAUD Committee proving that a chain reaction was possible. The MAUD Committee Report of 1941 concluded that a bomb could be built and recommended collaboration with the United States to do so.

After examining the report, the British Scientific and Advisory Committee judged the bomb to be high priority. They recommended that a pilot plant for the separation of U-235 be built in the U.K. followed by a full scale plant in Canada. Churchill asserted, “Although personally I am quite content with the existing explosives, I feel we must not stand in the path of improvement, and I therefore think that action should be taken…” (Farmelo 129). He thus created within the Department of Scientific and Industrial Research (DSID) the organization responsible for all atomic resources, the Directorate of Tube Alloys. Tube Alloys would be the code name for the British atomic project for the duration of the war.

Collaboration with the Manhattan Project

As the United States organized preliminary research and administration, British scientific work remained far ahead. When President Roosevelt wrote to Churchill in August 1941 suggesting collaboration, Churchill responded unenthusiastically, preferring to keep the more advanced Tube Alloys project separate. British leaders were also concerned with security. While Britain already had secrecy restrictions in place due to World War II, the British thought that the United States, not yet involved in the war, could be a liability. The irony of the situation, however, was that by this time the British project was already infiltrated by several Soviet spies including Klaus Fuchs, Donald Maclean, and Guy Burgess.

Nevertheless, by 1942 the two countries had completely switched positions regarding scientific progress. A scientific mission to the U.S. led by Wallace Akers, the director of Tube Alloys, visited the S-1 committee as well universities where preliminary research had begun. They were greatly impressed by the organizational abilities and scientific resources the Americans had built up. During another visit, Michael Perrin, the secretary-general of Tube Alloys, noted that the U.S. would “completely outstrip us in ideas, research and application of nuclear energy and that then, quite rightly, they will see no reason for our butting in” (Paul 28).

As the British realized the slow progress of their project, Halban’s Cambridge team was transferred to Canada in the summer of 1942. At Chalk River, this group would develop one of the first heavy water reactors in the world. Around the same time, Churchill agreed that the British and American projects should be merged and a diffusion plant built in the United States.

Churchill proposed a five point agenda for collaboration:

a free exchange of information should occur between the two nations

an agreement to not use the bomb against each other

an agreement to not use the bomb against other nations without consent of both

an agreement not to share information with other parties without the consent of both

the United States could have full use of British commercial and industrial capacities.

Despite resistance from United States advisors such as Vannevar Bush and James Conant, Churchill had a profound influence on President Roosevelt and the two eventually agreed to collaborate. In Quebec City on August 19, 1943, the two sides signed the Quebec Agreement, adopting most of Churchill’s five point plan. To ensure “full and effective collaboration,” the agreement established a Combined Policy Committee (CPC) with representatives from the U.S., the U.K., and Canada. It also gave the Manhattan Project the resources of British uranium, established a research center in Montreal, and ensured the participation of British scientists.

Many prominent British scientists were soon transferred to the United States to work on the Manhattan Project. The team of 19 scientists from the British project who worked at Los Alamos included Chadwick, Peierls, Fuchs, and William Penney. Nevertheless, General Leslie Groves, who disapproved of collaboration, put the British scientists in limited roles to restrict their access to complete information.

In September 1944, a second summit was held in Quebec City to discuss plans for the final assault on Germany and Japan. A few days later, Churchill and his family went to Roosevelt’s estate in Hyde Park, New York. The two leaders pledged in a memorandum, “Full collaboration between the United States and the British Government in developing Tube Alloys for military and commercial purposes should continue after the defeat of Japan unless and until terminated by joint agreement” (Goldschmidt 217).

Despite this promise, the death of Roosevelt in 1945 marked the end of wartime collaboration. President Truman chose not to abide by this second agreement, and United States nuclear research was formally classified in the 1946 Atomic Energy Act.

(Re)starting the British Project

The British had contributed to the successful creation of an atomic bomb, and yet after the war were faced with the reality that they had been cut off from its secrets. In 1947, Prime Minister Clement Attlee made the decision to independently pursue a British atomic bomb. A special cabinet committee quickly authorized “research and development work on atomic weapons” (Farmelo 318).

Lord Portal of Hungerford was put in charge overseeing of the project while William Penney, the British equivalent of J. Robert Oppenheimer, was the head scientist. During his time with the Americans, Penney had worked at Los Alamos, witnessed the Nagasaki bombing, and worked on Operation Crossroads. In May 1947 he was called to Whitehall and told by Lord Portal, “We’re going to make an atomic bomb. The Prime Minister has asked me to coordinate the work. They want you to lead it” (Farmelo 368)

Caption: William Penney

Although the Atomic Energy Act had classified United States atomic secrets, prominent British scientists who had worked on the Manhattan Project came back armed with information. Nevertheless, the efforts of General Groves to limit British involvement meant that no British scientists had a complete picture of the Manhattan Project. Therefore, one of the first actions Penney took was to draw up a document, entitled “Plutonium Weapon – General Description,” detailing the collective notes of all the British scientists who had worked on the project.

Administrative offices, known as “the cage” after the network of physical bars that surrounded them, were set up in London. Research centers were also established at Woolwich and Fort Halstead. The research was divided into three main areas: armaments, run by Penney himself; research, headed by John Cockcroft; and engineering, under Christopher Hinton. The engineering division itself was an enormous responsibility, as it included the construction of nuclear plants to produce usable plutonium.

The British bomb was based on the design of the American plutonium implosion bomb, using notes brought back by Penney and Fuchs. Fuchs, a Soviet spy, passed similar information to the Soviet project. Plutonium was primarily produced from Hinton’s reactors, although some was also imported from the Chalk River site in Canada. The first British plutonium plant was built at Sellafield, later renamed Windscale, in Cumberland. Its first production reactor went critical in 1950, and was producing usable plutonium by 1952.

Caption: British workers prepare a radio antenna for Operation Hurricane

Although the United States had classified its atomic secrets in 1946, negotiations continued to restart collaboration. These negotiations reached their apex in 1949, when the Soviet Union tested its first atomic bomb, giving the United States a heightened sense of urgency. Although the Department of Defense asserted that for Britain to be an equal in collaboration it would have to “fabricate a considerable number of atomic weapons” (Paul 182), the United States was considering a proposal that would have sent British scientists to work in the U.S. for a limited period of time. The hope was that the British scientists might spark new ideas in the US program, and that Britain would continue to supply uranium from the Congo.

Nevertheless a series of spy scandals in 1950 and 1951 ended any chance of collaboration. The revelations that Klaus Fuchs, Donald Maclean, and Guy Burgess were Soviet spies, as well as the defection of prominent nuclear scientist Bruno Pontecorvo, fueled anti-communist hysteria in the United States. The U.S. would even decline Britain’s request to test their first atomic bomb at Frenchman Flat in Nevada.

Winston Churchill, having returned as Prime Minister in 1951, negotiated to use the Australian island of Monte Bello as a testing site. The first British atomic bomb was successfully tested on October 3, 1952, during Operation Hurricane. It was detonated inside the hull of the HMS Plym, vaporizing the ship.

Shortly after the test, Churchill sent a telegram to Penney, Cockcroft, and Hinton thanking them for “the devoted efforts they have made and the brilliant engineering skill they have shown” (Farmelo 392). Penney was also knighted soon after. The British atomic bomb would be deployed for military operational use in 1953.

Further Development and Legacy

Caption: A British Polaris missile

Having tested their first atomic weapon, the British expected a return to collaboration with the United States. Less than a month later, however, the U.S. tested its first hydrogen bomb, once again putting it at a technological advantage and without any desire to share its nuclear secrets. In 1954, Churchill ordered that Britain commence with the development of thermonuclear weapons, and the U.K. successfully tested its first hydrogen bomb on November 8, 1957.

By this point, the Soviet Union was also in possession of the hydrogen bomb and had even advanced beyond American technological capabilities with the launch of the world’s first artificial satellite, Sputnik 1, in October 1957. Without a clear military advantage, the United States finally agreed in 1958 to share nuclear information with the United Kingdom by amending the Atomic Energy Act of 1946. The same year, the two sides also signed the U.S.-U.K. Mutual Defense Agreement, allowing collaboration on nuclear research as well as the transfer of materials and equipment.

After a brief moratorium on nuclear tests, the United Kingdom began conducting joint tests together with the United States in Nevada. British atomic weapons were subsequently modeled on American designs made available by the 1958 agreement. The U.K. also went on to purchase weapons from the U.S., including the submarine-based Polaris missile as well as American delivery systems. While today the United States and Russia each operate approximately 7,000 atomic weapons, Britain maintains the world’s fifth largest nuclear arsenal with 215 strategic warheads.