IAN BRUCE, Defence Correspondent September 04 2007
Britain has been allowed to share America's nuclear weapons technology since 1958 as part of a fairly one-sided defence pact, set up originally to counter the threat of a Soviet invasion of Western Europe.
It has since morphed into a dependency on American hardware, in exchange for cutting-edge British research data and spare high-grade plutonium, as early Polaris missile systems were replaced by Trident, and the range and capability of the armoury increased exponentially.
Although the UK ostensibly designs and builds its own warheads, they are based almost entirely on the ageing US W-76 blueprint.
Britain's four Vanguard-class missile submarines, known to their crews as "bombers", carry 16 Trident D5 missiles - each armed with three warheads capable of striking targets almost 5000 miles away within an accuracy of a few feet. The missiles are made in the US by Lockheed Martin and held as part of a shared US/UK pool of D5s at the American naval base at King's Bay, Georgia. Britain has access to 58.
The in-flight guidance for the missiles is also dependent on the US military satellite network, although they could be launched independently if a loss of accuracy was accepted.
Maintaining the UK nuclear deterrent costs about £1.6bn a year and is scheduled to rise to at least £2bn annually from 2008 as the first steps are taken to begin work on the replacement boats for the Vanguards announced earlier this year.
A squadron of three, perhaps four, new submarines are to be ordered at a cost of between £10-14bn to begin taking on the UK deterrent role from 2024.
The UK's Aldermaston site operates closely with the three main US weapons laboratories at Lawrence Livermore in California, and Sandia and Los Alamos in New Mexico.
Doubts over the reliability of the ageing W-76 warheads and the deterioration of some of their components two years ago led to the launch of a transatlantic project to find a robust and reliable replacement. Funding for the project has existed in the US since 2005.
In the absence of banned underground verification tests, some physicists claim three out of 10 of the old warheads would fail to explode in combat.
Although Aldermaston has, until recently, been starved of comparable financing to its US counterparts, US scientists say UK colleagues are ahead in certain technologies because they have been forced to be resourceful.