ship of her class, became the first British vessel to fire a Polaris. All Royal Navy SSBNs have been based at Faslane, only a few miles from Holy Loch. Although one submarine of the four was always in a shipyard undergoing a refit, recent declassifications of archived files disclose that the Royal Navy deployed four boatloads of reentry vehicles and warheads, plus spare warheads for the Polaris A3T, retaining a limited ability to re-arm and put to sea the submarine that was in refit. When replaced by the Chevaline warhead, the sum total of deployed RVs and warheads was reduced to three boatloads. Chevaline The original U.S. Navy Polaris had not been designed to penetrate anti-ballistic missile (ABM) defenses, 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. Britain's submarines featured the Polaris A3T missiles, a modification to the model of the Polaris used by the U.S. from 1968 to 1972. Similar concerns were present in the U.S. as well, resulting in a new American defense program. The program became known as Antelope, and its purpose was to alter the Polaris. Various aspects of the Polaris, such as increasing deployment efficiency and creating ways to improve the penetrative power were specific items considered in the tests conducted during the Antelope program. The British's uncertainty with their missiles led to the examination of the Antelope program. The assessments of Antelope occurred at Aldermaston. Evidence from the evaluation of Antelope led to the British decision to undertake their program following that of the United States. The result was a programme called Chevaline that added multiple decoys, chaff, and other defensive countermeasures. Its existence was only revealed in 1980, partly because of the cost overruns of the project, which had almost quadrupled the original estimate given when the project was finally approved in January 1975. The program also ran into trouble when dealing with the British Labour Party. Their Chief Scientific Adviser, Solly Zuckerman, believed that Britain no longer needed new designs for nuclear weapons and no more nuclear warhead tests would be necessary. Though the Labour party provided a clear platform on nuclear weapons, the Chevaline program found supporters. One such individual who supported modification to the Polaris was the Secretary of State for Defence, Denis Healey. Despite the approval of