Trident
The Polaris Sales Agreement was used as the model for the UK's purchase of the Trident weapon system to replace Polaris in British service. The arrangements were almost identical to that for Polaris, the United Kingdom procured the Trident system from America and fitted them to their own submarines, the Vanguard-class. HMS Vanguard entered operational service in December 1994.
British Prime Minister Margaret Thatcher had written to President Carter on July 10, 1980 to request that he approve supply of Trident I missiles. However in 1982 Thatcher wrote to President Reagan to request the United Kingdom be allowed to procure the Trident II (Trident D5) system, the procurement of which had been accelerated by the US Navy. This was agreed in March 1982.
Under the Polaris Sales Agreement, the United Kingdom paid a 5% levy on the cost of equipment supplied in recognition of US research and development costs already incurred. The R&D contribution to Trident comprised payments amounting to $116M with no on-going R&D levy. U.S. suppliers are paid via the U.S. based Polaris Trust Fund.
Read more about this topic: Polaris Sales Agreement