[6] During the 1950s, the UK's nuclear deterrent was based around the V-bombers of the Royal Air Force (RAF), but developments in radar and surface-to-air missiles made it clear that bombers were becoming increasingly vulnerable, and would be unlikely to penetrate Soviet airspace in the 1970s.

[9] The Royal Navy began seeking a nuclear role as early as 1945, when the Naval Staff suggested the possibility of launching missiles with atomic warheads from ships or submarines.

Its "carriers versus bombers" debate with the RAF resembled the similar inter-service dispute in the United States at this time that led to the "Revolt of the Admirals".

[13] The Defence Research Policy Committee (DRPC) considered the prospect of arming submarines with nuclear missiles, but its March 1954 report highlighted technical problems that it did not expect to be resolved for many years.

[15] Submarine propulsion research was suspended in October 1952 to conserve plutonium production for nuclear weapons, and by 1954 the Royal Navy had concluded that it would not be possible until the 1960s.

[21] Burke's support was crucial, as the United States Congress Joint Committee on Atomic Energy was uncertain about the legality of transferring such technology to the UK, and Rear Admiral Hyman G. Rickover, the head of the US Navy's nuclear propulsion project, was opposed.

[22][23] The British development of the hydrogen bomb, and a favourable international relations climate created by the Sputnik crisis, facilitated the amendment of the McMahon Act to permit this,[16] and the transfer of submarine reactor technology was incorporated in the 1958 US–UK Mutual Defence Agreement, which allowed the UK to acquire nuclear weapons systems from the United States, thereby restoring the nuclear Special Relationship.

The US Navy was involved in a cooperative venture with the US Army to develop the Jupiter missile, although there were concerns about the viability and safety of a liquid-fuel rocket at sea.

It not only implicitly addressed the drawbacks of Blue Streak in that it was not vulnerable to a pre-emptive nuclear strike, but invoked the traditional role of the Royal Navy, and its second-strike capability made it a more credible deterrent.

[34] In February 1958, Mountbatten created a working party to examine the effectiveness, cost and development time of Polaris compared with that of Blue Streak and the V-bomber force.

[43] A June 1960 paper by the Director General, Weapons, Rear Admiral Michael Le Fanu, recommended that a Polaris project should be created along the same lines as SPO.

[53] As had been feared, the President of France, Charles de Gaulle, vetoed the UK's application for admission to the EEC on 14 January 1963, citing the Nassau Agreement as one of the main reasons.

Bevan told his colleagues that their demand for unilateral nuclear disarmament would send a future Labour government "naked into the conference chamber" during international negotiations.

[73] A mission led by Sir Solly Zuckerman, the Chief Scientific Adviser to the Ministry of Defence, left for the United States to discuss Polaris on 8 January 1963.

An alternative proposal was to take the incomplete nuclear-powered hunter-killer submarine HMS Valiant, cut it in half, and insert the Polaris missile compartment in its midsection.

[85] Mackenzie, the Flag Officer Submarines (FOSM), was informed on 26 December 1962 that he would be appointed the Chief Polaris Executive (CPE);[86] the term was henceforth used to refer to both the man and his organisation.

To allow the Polaris Executive to be co-located, a block of single-storey prefabricated offices was built at Foxhill on the south side of Bath, which was occupied in February 1964.

[92] The interdependence between the two projects extended well beyond the shipyard; Valiant would be the first boat powered by the Rolls-Royce pressurised water reactor, which would also be used in the new Polaris ballistic missile submarines.

The JSTG was not an adversarial forum, but from the start there were disagreements over the scope of the Polaris Sales Agreement, which the staff of CPE saw as open-ended, but that of SPO saw as limited in nature.

[99] The firm was thoroughly familiar with the heightened requirements nuclear-powered submarine construction entailed in terms of cleanliness, safety and quality control, and the government had already spent £1.5 million upgrading the yard's facilities.

[111] Concerns about the Walney Channel proved justified; when the launch was delayed by half an hour due to a protest by the Campaign for Nuclear Disarmament, the falling tide left insufficient clearance, and the boat became stuck in the mud.

[112] The Cammell Laird boats had a reputation for not being as well built as those of Vickers,[113] which was a factor in the subsequent 1969 decision by the Treasury and the Royal Navy to restrict future nuclear submarine construction to a single yard.

[124] The government denied speculation that the Nassau Agreement permitted the addition of electronic mechanisms in the missile to give the United States a veto over its use.

[125] The A-3 missile that replaced the earlier A-1 and A-2 models in the US Navy had a range of 2,500 nautical miles (4,600 km) and a new Mark 2 weapon bay housing three re-entry vehicles.

It was believed that the MRV arrangement would also make the warhead harder to intercept with an anti-ballistic missile (ABM) similar to that of the American Nike Zeus system.

[139] The First Sea Lord, Admiral of the Fleet Sir Caspar John, denounced the "millstone of Polaris hung around our necks" as "potential wreckers of the real navy".

The proposal ran into opposition from the Supreme Allied Commander Europe (SACEUR), General Lyman Lemnitzer, who pressed on 2 January 1967 to have the Polaris boats assigned to NATO as promised under the Nassau Agreement.

[161] The result was Chevaline, an improved front end (IFE) that replaced one of the three warheads with multiple decoys, chaff, and other defensive countermeasures,[162] in what was known as a Penetration Aid Carrier (PAC).

[170] The Chief of the Defence Staff, Field Marshal Sir Michael Carver suggested giving up on the "Moscow criterion" and re-targeting Polaris to devastate less strongly defended cities.

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.