It must have been about 1982. The pews of the big church in Matlock were packed. A nervous Conservative MP for West Derbyshire, aged 32, was in the pulpit making the case, as I had been challenged to do, against the Campaign for Nuclear Disarmament. It was a case I believed then, voted for in the Lobbies and believe now.

This weekend we are just short of the 50th anniversary of the founding of CND. For the Radio 4 Archive Hour series next week I shall be presenting a programme about CND's half-century that draws on the rich resource of BBC interviews and commentary. Bertrand Russell, Canon John Colins, Hugh Gaitskell, Aneurin Bevan, Pat Arrowsmith and a very young Joan Bakewell all feature, and I have been able to talk to Margaret Thatcher's former Defence Secretary, Michael Heseltine. I reach no conclusions but, in the tradition of this series, try to let all sides speak.

In order to edge myself into a fairminded treatment of a position I know to be important but have always opposed, I have been conducting a sort of thought-experiment: trying hard to to make - to myself - the best case I can for the existence (over most of my lifetime) of a movement campaigning for unilateral nuclear disarmament.

CND's case must be distinguished from two others in particular. First, of course, most of us would argue for the desirability of multilateral disarmament, in which all nations agreed to try to reduce their nuclear stockpiles. But CND, much more controversially, has argued that nations should disarm whether or not this is matched by reciprocal disarmament by others.

Secondly, CND's argument must be distinguished from what we can call the defence-case argument against Britain's Trident system. Some defence experts question the practical cost-effectiveness (post-Cold War) and the genuine independence of Britain's “independent” nuclear weaponry, and argue that it might do better to leave larger allies to wield the nuclear umbrella.

Attracted by this case I cannot help thinking that if we diverted our nuclear budget into a vastly expanded and upgraded SAS, this could prove more useful to us in the world. But for CND to pray in aid this defence-case argument against Trident is disingenuous. It has always been, and must be, driven by a raw and principled objection to all nuclear arms - not a proposal for Britain to let others do the dirty work.

Arguably, CND (with its leftish and pacifist ideological baggage) has weakened the defence-case objection to Trident by association. I was one of those Tories who could have been attracted to the doubts about Trident on cost-efffectiveness grounds of Field Marshal Lord Carver - except that we didn't want to be lumped together with CND.

Its leadership has been dominated by people of left-wing views. Whether or not fellow-travellers were significant within CND, the organisation certainly included many who openly and in perfectly good faith took a benign view of the Soviet Union and didn't really see world communism as a big threat.

Such people were among CND's driving forces. The support it attracted, however, went beyond the Left. One of the reasons I responded to that invitation to speak in Matlock was that I sensed the anxiety widespread among ordinary voters - churchgoers in particular. American cruise missiles at Greenham Common, plus a vague feeling that the Tories were raising the stakes and ramping up the nuclear threat, worried plenty of doubtful Conservative voters, especially women and first-time voters. Perhaps a majority of Liberal and floating voters in my constituency were anxious too.

The official advice from government Whips was not to give CND a platform by agreeing to public debates; but I thought this mean-spirited and believed that the argument for Western nuclear preparedness was one we could win in the part of England I knew best: my constituency.

It was clear to me how. The overwhelming majority of my constituents in the 1980s accepted the argument that Michael Heseltine advanced for a nuclear balance: the argument that unilateral disarmament endangered peace and freedom because it invited attack.

Two things, however, unnerved them. First, the possibility of an accident arising from a genuine misunderstanding, technical malfunction or system-failure. Secondly, the possibility that in British or American politics a gung-ho political-military argument was gaining ground, or could do so. Voters were seriously bothered by sabre-rattling, and the emergence of politicians at Westminster and in Washington who saw nuclear weapons not as a ghastly necessity, but as an exciting possibility for enhancing global predominance. Stanley Kubrick's 1960s classic, Dr Strangelove or: How I Learned to Stop Worrying and Love the Bomb, kept its hold on the popular imagination. Kubrick achieved a grisly marriage of system-failure with atomic exuberance.

In the prevention of system-failure there is little that public anxiety can achieve. But democratic pressure does have a big part to play in the chilling of political and military exuberance. You may not have cared over the years (I didn't) for CND's Aldermaston marches, the sit-downs in Trafalgar Square, the encampment of women at Greenham Common. And in their history they have rarely pushed the poll numbers favouring disarmament over 50 per cent.

But the sizeable minority who support CND's case are ciphers for the suppressed worries that all of us share. By giving focus, expression and organisation to this persistent, if incipient, national alarm, CND has done something to thwart the growth of the kind of politics that can tip over into nuclear warmongering and ensured that Britain's advice at top tables has tended to be sober.

Mrs Thatcher's choice for her nuclear propagandist of Michael Heseltine, a thoughtful man of liberal and humane instincts whom she did not especially care for, spoke volumes. She knew voters were uneasy about cruise and later Trident. Our political class do not have an entirely free hand in these matters, and CND and its friends - though I may disagree with almost every argument they make - have played an honourable role in projecting to our leaders the popular mistrust of nuclear exuberance.

Henry Kissinger, no pacifist, has argued that fortune plays a greater role in history than we like to acknowledge. Because the Cuban missile crisis did not lead to war, we suppose that it was never a serious possibility, and that CND was always wrong. Well, in the event, perhaps, it was. But if nuclear war had happened - and it could have - we should be saying today that it had always been right. If, that is, we were alive to say it. Upon slender threads do arguments, later said to be palpably right or wrong, depend; and it is all more haphazard than we think.

50 Years of Ban the Bomb is broadcast on Radio 4, Saturday, January 26, at 8pm

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