Britain's Labour leaders have taken the Bush doctrine of pre-emption to heart. First, Tony Blair pre-empted his government's energy review and pronounced himself in favour of building new civil nuclear reactors, but at least he is prime minister and had already announced a review. Now, Gordon Brown, chancellor of the exchequer, has launched his own pre-emptive strike by pledging to retain the UK's nuclear deterrent beyond its current batch of Trident submarines, before he has yet become prime minister or a formal review of such a move is in train. The chancellor's motive was clearly to reassure Blairites on the right of the party that he would be a safe successor. But in doing so he is playing short-term politics with a strategic decision that has consequences for Britain and the world.

Much has changed since the early 1980s when the UK made its last nuclear weapon decision replacing US Polaris missiles with Trident ones on its submarines. Many of the changes argue for Britain abandoning the costly strategic nuclear capability it has maintained since the mid-1950s. Gone is the single looming menace of the Soviet Union that it helped deter. The new threats are far less likely to be checked by the cold calculus of deterrence: al-Qaeda-style terrorism and the emergence of new, and possibly less rational, nuclear weapon states such as North Korea and Iran, despite the prohibitions of the nuclear non-proliferation treaty. This treaty, too, enjoins Britain as well as the four other original nuclear powers to work towards abolishing their atomic arsenals. The fact that they have not is used as a pretext by other countries to slide out of their treaty obligations and has helped stymie disarmament progress. Finally, it can be argued that Britain could put the money spent on maintaining nuclear weapons it hopes never to use to far better ends in improving conventional military equipment for which it finds all too regular a use.