The British Blue Streak missile programme was in trouble by the late 1950s. The programme was too expensive and the missiles were to be housed in vulnerable silos near centres of population and expected to cause public anxiety.
The Blue Streak was cancelled in February 1960 and replaced by an agreement to purchase the American Skybolt missile. In 1962 the American Secretary of Defence, Robert McNamara, decided to scrap Skybolt and left Macmillan without a nuclear arms strategy. The submarine-based Polaris system was identified as a viable replacement (already in service with the American navy).
In December 1962, during further negotiations at Nassau, Macmillan demanded submarine-launched Polaris missiles for Britain. John F. Kennedy was reluctant, believing bilateral arrangements would hinder British entry to the European Economic Community (EEC), but eventually agreed to supply the missiles. With the decision to replace the V-bomber force with Polaris, control of the nuclear deterrent passed from the RAF to the Royal Navy. By 1968 the first of the strategic missile submarines was on deterrent patrol. The Royal Navy officially took over from the RAF in the middle of 1969 and since then there has always been at least one missile submarine on patrol.
During the Nassau negotiations, the Americans pressed for the establishment of a multilateral (or 'mixed-manned') North Atlantic Treaty Organization (NATO) nuclear force. Britain was opposed to this because of the cost - and its desire to prevent German access to nuclear weapons. In 1964 the British Prime Minister, Harold Wilson, succeeded in persuading the president of America, Lyndon B. Johnson, to consider an Atlantic Nuclear Force. It was designed to ensure Britain would retain control of its Polaris missiles while appearing to give up an independent deterrent. In the end this proposal was abandoned. Polaris went to sea as an American-designed missile in a British-designed submarine with a British warhead - under British control.
From the mid-1970s it was clear that Polaris required improvements to present a viable deterrent in the face of improving anti-ballistic missile systems. The Heath government embarked on an ambitious project called Chevaline to improve Polaris without American assistance. The project was lengthy and expensive but was continued by the Labour government under Wilson and Callaghan and then by the Conservatives under Margaret Thatcher. Such was the secrecy surrounding the Chevaline project it was never discussed formally at Cabinet and was only admitted to in 1980 in a wide-ranging parliamentary debate on improvements to NATO's nuclear forces.
The strategic weapons of V-bomber force and Polaris missile submarines were not the only nuclear weapons deployed by the British. A range of tactical nuclear weapons were also deployed by the Navy, RAF and Army, ranging from nuclear depth charges to attack hostile submarines, free-fall nuclear bombs delivered by jets to short range missiles operated by the Army. However, once the decision to acquire strategic nuclear weapons was made, there was no discussion at Cabinet level about the use or acquisition of 'minor' tactical atomic weapons.