"Subtle as an air raid” might be a good way to describe the galumphing political semaphores now coming from Gordon Brown. He hopes that they will reshape our ideas about him before he assumes the prime ministership. Last week his arms were flapping vigorously to signal that despite being thought a figure of the left he can be relied upon to renew Britain’s nuclear deterrent.

If that is his reasoning, the chancellor is thinking in oldspeak. Being for or against the renewal of Britain’s deterrent now has nothing to do with right and left as it once did. In a depressing way, all too common in British politics, Brown’s policy for the future does not reflect fresh or even modern ideas about the issue. It is rather a reaction to his party’s past.

Labour has in its time suffered appalling anguish over nuclear weapons. The party’s Christian socialists found the idea of mass human destruction utterly repugnant and believed that Labour had a duty to renounce Britain’s deterrent. Some campaigners were utopian pacifists, others were inspired by anti-Americanism and a few were communist sympathisers at a time when British missiles were targeted against the Soviet Union.

Even so, it has fallen to Labour in office to take critical decisions that made Britain a nuclear power and kept it so. It was Ernest Bevin, a Labour foreign secretary, who first memorably concluded that the bomb needed to have a Union Jack on it.

A recurring theme in the party’s history is that those who become its leaders renounce their earlier commitment to disarmament. Nye Bevan, a founder of Tribune magazine which led the anti-nuclear campaign, went on to be shadow foreign secretary and then urged the 1957 Labour conference to reject a unilateralist motion, because it would “send a British foreign secretary . . . naked into the conference chamber”.

The Labour manifesto for the 1964 election remarked that the Polaris submarine-launched deterrent “will not be independent and it will not be British and it will not deter”. Nonetheless Harold Wilson, who won that election for Labour, oversaw the system’s introduction.

Tony Blair’s campaign leaflet in his unsuccessful attempt to win Beaconsfield in the 1982 election reminded voters that “Labour is the only party pledged to end the nuclear madness”. Brown told parliament two years later that Trident, which replaced Polaris, was “unacceptably expensive, economically wasteful and militarily unsound”.

One Labour leader, Michael Foot, did remain committed to unilateral disarmament. His policy contributed substantially to Labour’s slaughter in the 1983 general election. Neil Kinnock, his successor, learnt the lesson and ditched Foot’s policy — and maybe his own principles as well.

The youthful Blair was wrong. Mutually assured destruction was frightening but not insane. In the days when the Soviet Union aspired to dominate the world and was equipped to destroy the West’s capital cities, only the near-guarantee that it, too, would be obliterated provided us with security.

Furthermore, in case the Russians might think that they could devastate European capitals (as part of an overland assault on western Europe) without luring America into a nuclear exchange, Britain had to have its own weapons system. That complicated the calculation for the Russians; hidden beneath the ocean on a submarine, the British deterrent could not be eliminated in a first strike. Brown was wrong, too, about the cost of deterrence. Britain could buy nuclear security for just a small part of the defence budget.

Two decades later we live in a different world and the arguments ought to have changed. We face no threat from the Soviet Union. The nuclear weapons states that we might fear, such as North Korea, China and in the future Iran, have much less developed systems than the Russians. Unlike the Soviet Union they do not have tank divisions in Germany and Czechoslovakia ready to race towards Frankfurt. It is not easy for them to blackmail us, still less attack us.

If somehow they could threaten us, it is hard to see how Britain’s own weapons could deter them. As Wilson observed after he had left Downing Street: “I never believed that we had a really independent deterrent.” Britain relies for its technology on the United States and it is inconceivable that we could use our weapons without American permission. That being so, Britain’s “independent” deterrent becomes ineffective.

Our enemies know, too, that democracies can use nuclear weapons only if they have come under nuclear attack. Even when Britain has felt that its vital national interests were threatened it could not even contemplate a nuclear response. So Colonel Nasser of Egypt did not hesitate to nationalise the Suez Canal, nor did Argentina’s General Galtieri think twice about invading the Falkland Islands.

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