page_title: Polaris (UK nuclear programme)
section_title: Upgrades
hierarchical_section_title: Polaris (UK nuclear programme) / Upgrades
caption_attribution_description: Photo of Polaris A3 missile taken at the RAF Museum Cosford, Shropshire, England.
context_page_description: The United Kingdom's Polaris programme, officially named the British Naval Ballistic Missile System, provided its first submarine-based nuclear weapons system. Polaris was in service from 1968 to 1996.
  Polaris itself was an operational system of four Resolution-class ballistic missile submarines, each armed with 16 Polaris A-3 ballistic missiles. Each missile was able to deliver three ET.317 thermonuclear warheads. This configuration was later upgraded to carry two warheads hardened against the effects of radiation and nuclear electromagnetic pulse, along with a range of decoys.
  The British Polaris programme was announced in December 1962 following the Nassau Agreement between the US and the UK. The Polaris Sales Agreement provided the formal framework for cooperation. Construction of the submarines began in 1964, and the first patrol took place in June 1968. All four boats were operational in December 1969. They were operated by the Royal Navy, and based at Clyde Naval Base on Scotland's west coast, a few miles from Glasgow. At least one submarine was always on patrol to provide a continuous at-sea deterrent.
context_section_description: The original US Navy Polaris had not been designed to penetrate ABM defences, but the Royal Navy had to ensure that its small Polaris force operating alone, and often with only one submarine on deterrent patrol, could penetrate the ABM screen around Moscow. The Americans upgraded to Poseidon, which had MIRV warheads. Although it suffered from reliability problems that were not completely resolved until 1974, it represented a clear improvement over Polaris, and became the preferred option of the AWRE and the Admiralty. While it could not be carried by the ten George Washington- and Ethan Allen-class boats, it could be accommodated on the British Resolution class. Zuckerman attended a meeting with Rear Admiral Levering Smith, the director of SPO, and John S. Foster, Jr., the director of the Lawrence Livermore National Laboratory, at which the provision of Poseidon to the UK was discussed. While the cost was a factor, the main obstacle was political, and the Wilson government publicly ruled out the purchase of Poseidon in June 1967. Without an agreement on improvement, the Special Relationship began to decay. The Americans were unwilling to share information about warhead vulnerability unless the British were going to proceed to applying it.
  The result was Chevaline, an improved front end (IFE) that replaced one of the three warheads with multiple decoys, chaff, and other defensive countermeasures, in what was known as a Penetration Aid Carrier (PAC).  It was the most technically complex defence project ever undertaken in the United Kingdom. The system also involved "hardening" the warheads—making them resistant to the effects of a nuclear electromagnetic pulse (EMP). The Americans used a material known as 3DPQ, a phenolic thermosetting material infused with quartz fibres, in the heat shield of the warheads, which also acted as a defence against irradiation. Its adoption by the British warhead saved on research, but required a redesign of their warhead. The new warhead was designated the A-3TK, the old one being the A-3T. In 1972 Chevaline was estimated to cost £235 million. Agreement was reached with the Americans to conduct another series of tests in Nevada. The first of these, Arbor/Fallon, was conducted on 23 May 1974.
  By 1975, the cost of Chevaline had risen to £400 million, but it was protected from the budget cuts that affected the rest of defence spending by its own secrecy. Its main technical problem was that the PAC was heavier than the warhead it replaced, which reduced the range of the entire missile. This drove debate about the number of decoys that were required. 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. This was regarded as politically and militarily problematic, but was reluctantly accepted. At the same time, the government elected to press on with Chevaline. Another test, Anvil/Banon, was conducted in Nevada on 26 August 1976. By 1979, the cost had risen to £935 million, with test firings conducted from the Eastern Test Range and the Woomera Test Range, including three off Cape Canaveral by Renown,  along with another series of nuclear tests in Nevada.
  Chevaline's existence, along with its formerly secret codename, was revealed by the Secretary of State for Defence, Francis Pym, during a debate in the House of Commons on 24 January 1980. Sea trials were held in November 1980. The system became operational in mid-1982 on Renown, followed by Revenge in 1983, Resolution in 1985, and Repulse in 1987. One hundred A-3TK warheads were produced between 1979 and 1982. The final cost reached  £1,025 million. However, the Public Accounts Committee noted that due to inflation, £1 billion in April 1981 (equivalent to £3.01 billion in 2016) was not significantly greater than £235 million in April 1972 (equivalent to £2.6 billion in 2016). What disturbed the committee more was that a major project had gone on for a decade without any disclosure of its costs to Parliament or any require
caption: Polaris missile at the RAF Museum Cosford with Chevaline (centre, on yellow trolley)
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