A recent response added to the HM Treasury disclosure log:
Text of request:
How much does the UK pay to the USA for Trident missiles? What are the terms of agreement with the USA?
Text for disclosure:
Cost of procurement of Trident II D5 (unarmed) missiles up to 2004-05 provided in the attached file, this information has been previous supplied by MOD as answers to Parliamentary Questions.
The terms of agreement can be found in the Polaris Sales Agreement. This was signed in 1963 and published by HMSO (ISBN 0105468908), and is the Treaty under which the UK purchased Polaris and later Trident. A photocopy (priced £6) can be obtained by contacting The Stationery Office. Website www.tso.co.uk; e-mail email@example.com; and telephone 020 7873 8447.
PDF of Procurement cost of Trident II D5 (unarmed) missiles