the program, the expenses caused hurdles that augmented the time it took for the system to come to fruition. The cost of the project led to Britain's revisit of disbanding the program in 1977. The system became operational in mid-1982 on , and the last British SSBN submarine was equipped with it in mid-1987. Chevaline was withdrawn from service in 1996. Though Britain adopted the Antelope program methods, no input on the design came from the United States. Aldermaston was solely responsible for the Chevaline warheads. Replacement The British did not ask to extend the Polaris Sales Agreement to cover the Polaris successor Poseidon due to its cost. The Ministry of Defence upgraded its nuclear missiles to the longer-ranged Trident after much political wrangling within the Callaghan Labour Party government over its cost and whether it was necessary. The outgoing Prime Minister James Callaghan made his government's papers on Trident available to Margaret Thatcher's new incoming Conservative Party government, which took the decision to acquire the Trident C4 missile. A subsequent decision to upgrade the missile purchase to the even larger, longer-ranged Trident D5 missile was possibly taken to ensure that there was missile commonality between the U.S. Navy and the Royal Navy, which was considerably important when the Royal Navy Trident submarines were also to use the Naval Submarine Base Kings Bay. Even though the U.S. Navy initially deployed the Trident C4 missile in the original set of its Ohio-class submarines, it was always planned to upgrade all of these submarines to the larger and longer-ranged Trident D5 missile—and that eventually, all of the C4 missiles would be eliminated from the U.S. Navy. This change-over has been completely carried out, and no Trident C4 missiles remain in service. The Polaris missile remained in Royal Navy service long after it had been completely retired and scrapped by the U.S. Navy in 1980–1981. Consequently, many spare parts and repair facilities for the Polaris that were located in the U.S. ceased to be available (such as at Lockheed, which had moved on first to the Poseidon and then to the Trident missile). Italy During its reconstruction program in 1957–1961, the was fitted with four Polaris missile launchers located in the aft part of the ship. The Italian usage of Polaris missiles was partially the result of the Kennedy administration. Prior to 1961, Italy and Turkey were equipped with Jupiter missiles. Three factors