For a long time it was a very powerful force. It had its prophets and priests. Those who didn't conform to its precepts and its world vision were marginalised and even ridiculed. It is not yet dead but the signs of its mortality are very clear. It was the religion of nuclear peace. Nuclear weapons, so the priests and prophets claimed, had magical properties. If we possessed them then peace was more or less guaranteed. If we did not then the future would be perilous: the Soviet dragon would get us.

Later on, when and if that dragon retreated, some future mini-dragon might appear. That possibility had to be always guarded against. It was a religion which dominated the media, politics, and both faith and non-faith systems alike. Its adherents came from all ends of the spectrum from atheists and agnostics through to religious fundamentalists of all varieties.

Is such old thinking about nuclear weaponry really on its way out? It was Einstein who said: “Everything has changed except our modes of thinking, and thus we drift towards unparallel disaster”. Perhaps he would now hope that old nuclear convictions have passed their sell by date.

The most evident sign of this shift has come with Barack Obama. I have been in the nuclear weapons abolition field for over 50 years. For 50 years we have been fobbed off with rhetoric about supposed reductions. This was no more than economic good housekeeping. It did not raise the question of abolition. Now at last we have a world leader who has made the elimination of all nuclear weapons everywhere one of his goals. He could not have been clearer about his ultimate vision in Cairo in May 2009 .

More than that, he has taken positive steps himself. Steep cuts are under discussion with the Russians. No funds for yet another proposed US warhead. Abandonment of a missile shield in Poland and the Czech Republic. He has even done the near impossible: acknowledged that Israel is a nuclear weapon state and must be part of future abolition negotiations.

The old religion always ignored legal obligations, but they are there in the Non-Proliferation Treaty of 1968 with its clear commitment in Article VI to negotiating nuclear disarmament. Even more forcefully that legal obligation was stressed by the International Court in 1996 which ruled that "there exists an obligation to pursue in good faith and bring to a conclusion negotiations leading to nuclear disarmament in all its aspects under strict and effective international control".

Another nail has been driven into the coffin of old dogmas with the publication of a draft convention which covers all the issues that those negotiating abolition will have to face. They include setting up a nuclear inventory, outside inspection on demand, a verification agency of the United Nations with international powers, the criminalisation of anyone trying to develop or acquire nuclear weapons, and international legal protection to be given to whistle-blowers. A future Vanunu will hopefully not have to spend 18 years in prison.

The old religion depended on many assumptions all of which are now challenged. One such was that nuclear weapons - and there still are about 27,000 in the world - are safe. The long list of accidents which have occurred since 1945 were simply ignored. Worse, human misperceptions which led to near catastrophe were never given the publicity they should have had.

It is too long a story to tell here, but I think it highly likely that we humans owe our continued existence to a Colonel Petrov who refused to tell his superiors in 1983 what he thought he was seeing - a major missile attack on the Soviet Union. Had he done so the odds on World War III would have been high indeed.

Only this year a major disaster by a hair's breadth did not happen in the Atlantic. Had two submarine, one British and one French been a few metres closer they would have had a catastrophic head-on collision. Both would have sunk. Apart from nuclear pollution would warheads have exploded? Thankfully we did not have to find out.

The old religion had only one threat in mind: a military attack from another country which, it was believed, could be deterred by nuclear weapons. Now it is terrorists who are said to threaten us and we have come to realise that deterrence cannot work, if it worked at all, against suicidal people or those without a territorial base. No one ever suggested nuking Dublin or Belfast as a means of intimidating the IRA.

“Forty years of peace” they chanted to each other across the tables aisles on Newsnight and Panorama. Apart from the obvious fact that wars are not inevitable or compulsory, the Nato/Warsaw Pact nuclear cold war stand-off simply meant that hot conflict was transferred to satellite countries: Afghanistan, Angola, Nicaragua, Vietnam and the rest. Millions died as a by-product of nuclear deterrence and the cold war between the two blocs.

Finally, many have lost faith in the old religion because they simply can not see why it is reasonable to claim that some countries can have nuclear weapons but others cannot. What sin might Iran be committing that Britain has not already committed? The silly nationalism which led Ernest Bevin to push us down the nuclear road in 1947 is still alive and well even in late comers like India and Pakistan. If nuclear weapons mean status then all want status. But nuclear proliferation is clearly a road to a less, not more, secure world.

The problem with a dying religion is that too many have invested careers and reputations in it. Its priests and prophets know well that banging the nationalist drum in the Mail or the Telegraph will conjure up all sorts of ancient myths - even the Napoleonic one. This can still be heard in the corridors of Whitehall. How could we get rid of ours and take the risk that the French might be the only ones left with an independent nuclear weapons in Europe?

Not that ours are independent anyway. The “Moss Bros” deterrent Harold Wilson once called ours. And how right he was. Do many people know that we actually borrow our Trident missiles from the United States, return them for repair and get another set in exchange.

How can we British help the world to move towards a global understanding that common security based on interdependence is the only security to be had? It is a good moment to ask that question. Our country is at a cross roads. We either spend billions, perhaps £75 billion, on replacing our Trident nuclear submarine fleet or we become the first of the major nuclear powers to give up nuclear weapon status. A choice has to be made. No nonsense please about 3 submarines instead of 4: that is a purely cosmetic device designed to placate old believers who find change too difficult.

To say "NO" to Trident replacement would release massive sums of money which would ease our present economic crisis and enable a variety of humane and positive projects to go ahead. Internationally we would be giving strong support to Obama at a time when he much needs it and great encouragement to those participating in next May's NPT review conference of the NPT in New York.

Einstein was wrong. Old modes of thinking do change and we can help to speed up the process. As the Final Report of the First United Nations Special Session on Disarmament in 1978 said "Enduring international peace and security cannot be built on the accumulation of weaponry by military alliances nor be sustained by a precarious balance of deterrence or doctrines of strategic superiority".

It is time to move to a religion of common humanity, global law, mutual security and social and environmental responsibility.

2009