Leading article: Wise words, but the die is cast

The news that Hans Blix is lecturing today in Britain on nuclear weapons must surely raise at least a few hackles on the back of the Prime Minister's neck, for this is Round Two of the Blair versus Blix contest. Round One saw the former UN weapons inspector in Iraq urging Tony Blair and George Bush not to jump to conclusions about Saddam Hussein's weapons of mass destruction. Messrs Blair and Bush famously knew better and the rest is history.

So it is with a certain déjà vu that one senses the outcome of Round Two, in which Mr Blix will urge certain countries - no prizes for guessing which - not to update and develop their nuclear weapons systems, pointing out that they are undermining the Non-Proliferation Treaty and fuelling enormous resentment among nuclear "non-haves".

As before, Mr Blair will say he knows better. So will Parliament. Forget any idea of a real debate there. All the big guns in the Labour hierarchy, from Gordon Brown down, have lined up behind the Prime Minister on this issue. The Tories will also cheer on Mr Blair. Prepare for grandiose talk about how an updated Trident enables us to keep "punching above our weight", maintain "a seat at the top table", and all the other tired old phrases.

But once again it is Mr Blix who is right and Mr Blair who is wrong on the subject of weapons of mass destruction. Firstly, the modernisation of Trident is ruinously expensive. Even worse, it is money wasted, for most military strategists do not believe a Cold War system, designed to hit fixed targets in the Soviet Union, has much to offer us in this very different era. Trident offers no answer to - or security against - the challenges posed by rogue states and mobile, cell-based terrorist groups, some operating within, as well as outside, the West. One wonders what enemy Mr Blair has in mind when he insists a new Trident remains so essential to Britain's defence needs.

Domestic political considerations rather than long-term strategic thinking play a significant role in this decision. Mr Blair lacks the courage to be the man who pulled the plug on Britain's nuclear weapons, while the French cling like limpets to theirs and conventional wisdom says this is the only way to be a player on the global diplomatic stage. Never mind that is a useless deterrent. Never mind that Britain cannot use these weapons without the agreement of the US. Never mind the hypocrisy of encouraging other nations down the non-nuclear route even as we blow billions on the latest models.

It doesn't matter now, and nor ultimately do Mr Blix's wise words, for the die is cast. It is a shame, of course - Britain should be leading the way in lowering the nuclear threshold. Instead we are raising it.