The British government likes to tell us that Trident is an independent nuclear weapons system. The reality is, however, that it is entirely dependent on the United States – both technically and politically.
The US and the UK signed the Mutual Defence Agreement (MDA) in 1958, a bilateral treaty on nuclear weapons cooperation under which both countries agreed to exchange classified information to develop their respective nuclear weapon systems. The relevant part of the MDA is reviewed and renewed every ten years, most recently in 2014 where the process took place with no parliamentary debate or scrutiny. The treaty permits ‘the transfer between the United States and the United Kingdom of classified information concerning atomic weapons; nuclear technology and controlled nuclear information; material and equipment for the development of defence plans; training of personnel; evaluation of potential enemy capability; development of delivery systems; and the research, development, and design of military reactors’.
As a result of this treaty, the UK’s nuclear weapons system is highly reliant on the US. The system comprises three components: the submarines, the missiles and the warheads. The Trident missiles give their name to the system as a whole. These missiles are leased from the US, and the submarines have to return regularly to the US base in King’s Bay, Georgia, for the maintenance and replacement of the missiles. The UK pays an annual contribution of £12 million towards the cost of this base.
While the Vanguard-class submarines are made in the UK – at the Barrow-in-Furness shipyard in Cumbria – many aspects of the design are based on US nuclear submarines. Additionally, many of the system’s components are bought from the US. The gas reservoirs of the warheads are likely produced in the US, and are certainly filled with tritium there. The body shell, which contains the warhead, is purchased from the US; and the guidance system used by the Trident system is designed and made by Charles Stark Draper Laboratories, also in the US.