TONY Blair has opened the debate about the renewal of our Trident nuclear deterrent and already the usual suspects are turning up on the BBC and in all the papers to say we don't need it.

Their argument is that, though the bomb was required in the past to deter Soviet Russia, it is not needed now that the USSR has collapsed. Im reminded of some words from TS Eliot: Do you think that lions no longer need keepers?. Are we to suppose that Russia is no longer a threat? On the contrary, Russia is a more dangerous place under Mr Putins regime than ever it was under the Politbureau.

And it is still armed to the teeth with nuclear weapons.

In fact the whole world has become a more dangerous place since the downfall of communism in the late 1980s. Pakistan has acquired the nuclear bomb and, only this morning, I was reading the words of a senior defence consultant who fears that Pakistan, notoriously unstable, could easily fall into the hands of Muslim fundamentalists who hate President Musharraf for his siding with America after 9/11.

And then there is the little matter of President Ahmadinejad of Iran who has declared that he wants to wipe Israel off the map and do the same to Israels allies. Mr Ahmadinejad is quietly manufacturing nuclear weapons.

You might almost say that the case for possessing nuclear weapons has been won for the single reason that the Archbishop of Canterbury and most of the bishops are against them.

Politics in general and national defence in particular are not about idealistic moral abstractions: they are about interests. The British government has the overriding duty to act in the interests of the British people.

And it is not in our interests for us to become defenceless against potential enemies who are armed with nuclear weapons. The Labour Prime Minister Clement Attlee knew this in the 1940s and defied the unilateral disarmers in his own party by saying: I will not go naked into the conference chamber.

Whatever we may decide, you can be sure that Russia will not give up its nuclear weapons, and neither will Pakistan. Iran will not stop its bid to obtain the bomb. Of course, we know that nuclear weapons are very nasty things. But nasty things dont go away when we close our eyes, as if we were children afraid of the dark.

There is an analogy here. Remember whenever there's a particularly terrible series of gun or knife murders C what the tabloids call a massacre C governments resort to fatuous and futile gestures such as banning guns and knives. This is stupid and self-defeating, for when knives and guns are banned then the only people who retain these weapons are criminals who, of course, ignore the ban.

If we get rid of our nuclear weapons, then the only people in possession of them will be our enemies.

Or do the bishops and the CND members think that the likes of a lawless Russia, a fundamentalist Pakistan or a crazy demagogue in Iran will be so impressed by our unilateralism that they too will give up the bomb?

The daftest argument of the lot, and the biggest lie, is that without the bomb we would be safer. Remember this: the only country ever to have the bomb dropped on it is Japan C a nation which itself did not possess a nuclear deterrent.

Peter Mullen is Rector of St Michaels, Cornhill, in the City of London, and Chaplain to the Stock Exchange.