The agreement allows the United States and the United Kingdom to exchange classified information to improve the « ability to improve the development and production of nuclear weapons » on each side.  Although the United States has nuclear cooperation agreements with other countries, including France and some NATO countries, none of them resemble the mutual defence agreement between the United States and the United Kingdom.  Macmillan called it « the grand prize. »  Under the agreement, between 1960 and 1979, 5.37 tonnes of plutonium produced in the United Kingdom, compared to 6.7 kg of tritium and 7.5 tonnes of IU, were shipped to the United States. An additional 470 kg of plutonium was traded between the United States and the United Kingdom from an as yet unexplained subcontract.  Some of the plutonium produced in the United Kingdom was used by the United States in 1962 for the only known nuclear test of the reactor plutonium.  The plutonium shipped to the United States contained some produced in Magnox civilian reactors in the United Kingdom, and the United States assured that civilian plutonium was not used in the U.S. nuclear weapons program. It has been used in civilian programs that included California production and reactor research.  Article 3 provided for the sale in the United Kingdom of a complete nuclear submarine propulsion facility and the uranium needed for fueling for ten years.  Due to JCAE`s concerns, the AEC would determine the price Britain would pay for highly enriched uranium (HEU).  Originally, the treaty did not provide for non-nuclear elements of nuclear weapons to be transferred to Britain. It was amended on 7 May 1959 to allow Britain access to non-nuclear components and to allow the transfer of specific nuclear materials such as plutonium, HEU and tritium.
 The contract paved the way for Polaris` subsequent sales contract, which was signed on April 6, 1963.  The two agreements have been « the cornerstone of nuclear relations between Britain and the United States » for nearly 60 years.  At the end of 1947, 1,900 tonnes of uranium ore from the Belgian Congo were stored for the Combined Development Trust in Springfields, near Preston, Lancashire, as part of a war-sharing agreement and 1,350 tonnes (1,370 tonnes) for British use. In order to gain access to the stockpiles of their own nuclear weapons project, the Americans opened negotiations leading to the modus vivendi an agreement signed on January 7, 1948, which officially terminated all previous agreements, including the Quebec Agreement. it abolished the British right to consultation on the use of nuclear weapons;  allowed for a limited exchange of technical information between the United States, the United Kingdom and Canada, and sued the Combined Policy Committee and the Combined Development Trust, although the latter was renamed the Combined Policy Agency.   The main thing was that he secured the support of Carl T.