The British hydrogen bomb programme demonstrated Britain's ability to produce thermonuclear weapons in the Operation Grapple nuclear tests in the Pacific, and led to the amendment of the McMahon Act.

The US also supplied the Royal Air Force and British Army of the Rhine with nuclear weapons under Project E in the form of aerial bombs, missiles, depth charges and artillery shells until 1992.

[9] George Paget Thomson, at Imperial College London, and Mark Oliphant, an Australian physicist at the University of Birmingham, were tasked with carrying out a series of experiments on uranium.

[10] Oliphant delegated the task to two German refugee scientists, Rudolf Peierls and Frisch, who ironically could not work on the university's secret projects like radar because they were enemy aliens and therefore lacked the necessary security clearance.

Sir John Anderson, the Lord President of the Council, became the minister responsible, and Wallace Akers from Imperial Chemical Industries (ICI) was appointed the director of Tube Alloys.

[19] In July 1940, Britain had offered to give the United States access to its scientific research,[20] and the Tizard Mission's John Cockcroft briefed American scientists on British developments.

[24] On 30 July 1942, Anderson advised the Prime Minister of the United Kingdom, Winston Churchill, saying: "We must face the fact that ... [our] pioneering work ... is a dwindling asset and that, unless we capitalise it quickly, we shall be outstripped.

"[25] The British considered producing an atomic bomb without American help, but it would require overwhelming priority, would disrupt other wartime projects, and was unlikely to be ready in time to affect the outcome of the war in Europe.

It included distinguished scientists such as Geoffrey Taylor, James Tuck, Niels Bohr, William Penney, Frisch, Ernest Titterton and Klaus Fuchs, who was later revealed to be a Soviet spy.

[37] He served as a member of the target committee established by Groves to select Japanese cities for atomic bombing,[38] and on Tinian with Project Alberta as a special consultant.

Although Truman supported the proposal, several key officials, including the United States Atomic Energy Commission's Lewis Strauss and Senator Arthur Vandenberg, did not.

[88] After Britain developed nuclear weapons through its own efforts, the engineer Sir Leonard Owen stated that "the McMahon Act was probably one of the best things that happened ... as it made us work and think for ourselves along independent lines.

During Operation Hurricane, an atomic bomb was detonated on board the frigate HMS Plym anchored in a lagoon in the Monte Bello Islands in Western Australia on 3 October 1952.

49 Squadron RAF piloted by Edwin Flavell became the first British aircraft to drop a live atomic bomb when a Blue Danube was exploded over Maralinga, South Australia during Operation Buffalo.

Two British scientists, Egon Bretscher and Klaus Fuchs, had attended the conference there on the Super (as it was then called) in April 1946, and Chadwick had written a secret report on it in May 1946,[111] but the design was found to be unworkable.

In 1947, the Chiefs of Staff stated that even with American help the United Kingdom could not prevent the "vastly superior" Soviet forces from overrunning Western Europe, from which Russia could destroy Britain with missiles without using atomic weapons.

[171] At the three-power Bermuda Conference with Eisenhower in December 1953, Churchill suggested that the United States allow Britain to have access to American nuclear weapons to make up the shortfall.

[172] The provision on American weapons was called Project E.[173] The agreement was confirmed by Eisenhower and Macmillan, who was now the Prime Minister, during their March 1957 meeting in Bermuda,[174][175] and a formal Memorandum of Understanding (MOU) was signed on 21 May 1957.

[227] Up to 48 Red Beards were secretly stowed in a highly secured weapons storage facility at RAF Tengah in Singapore between 1962 and 1971 for possible use by V bombers and for Britain's military commitment to SEATO.

[245] In London, over one hundred Conservative members of Parliament, nearly one third of the parliamentary party, signed a motion urging Macmillan to ensure that Britain remained an independent nuclear power.

[247] In the end, Kennedy did not wish to see Macmillan's government collapse,[248] which would imperil Britain's entry into the European Economic Community (EEC),[249] so a face-saving compromise was reached: the US agreed to provide the UK with Polaris missiles, which would be assigned to NATO,[250] and could be used independently only when "supreme national interests" intervened.

[299] The government released a written statement on 25 February 2020, outlining that the UK nuclear warheads will be replaced and will match the US Trident II SLBM and related systems.

[89] It was followed by the first nuclear tests on the Australian mainland, which were conducted at Emu Field in the Great Victoria Desert in South Australia as part of Operation Totem on 14 and 26 October 1953.

Membership leapt from 3,000 in 1980 to 50,000 a year later, and rallies for unilateral nuclear disarmament in London in October 1981 and June 1982 attracted 250,000 marchers, the largest ever mass demonstrations in the UK up to that time.

[366] In a January 2015 written statement, Defence Secretary Michael Fallon reported that "all Vanguard Class SSBNs on continuous at-sea deterrent patrol now carry 40 nuclear warheads and no more than eight operational missiles".

"[373] Denis Healey, the Secretary of State for Defence and "alternate decision-taker" under Harold Wilson, said that in the event of Soviet nuclear weapons attacking the United Kingdom and the Prime Minister had been killed or incapacitated, he would not have ordered a retaliation.

[373] The precise details of how a British Prime Minister would authorise a nuclear strike remain secret, although the principles of the Trident missile control system are believed to be based on the plan set up for Polaris in 1968, which has now been declassified.

At the end of the Cold War the US Fail Safe Commission recommended installing devices to prevent rogue commanders persuading their crews to launch unauthorised nuclear attacks.

[377] The programme also addressed the workings of the system; detailing that two individuals are required to authenticate each stage of the process before launching, with the submarine captain only able to access the firing trigger after two safes have been opened with keys held by the ship's executive and weapons engineering officers.

"[391] During the Cold War, if a nuclear attack had taken place and the Prime Minister and their deputies could not be reached, then Royal Air Force Strike Command had standing delegated authority to retaliate.