I have always feared that Michael Foot and I have at least one weakness in common. Both of us find it almost impossible to accept Oliver Cromwell's advice and at least consider the possibility that we might be wrong. So it is not surprising that, having been on opposite sides of what Foot calls the 'often ferocious but still honourable disputes' about the nuclear deterrent, we should interpret the history of the period quite differently. I judge - relying on the evidence of Soviet behaviour, from Berlin in 1948 to Prague in 1968 - that the balance of terror kept the peace. Foot clearly regards those twenty years as two decades of lucky escape - a time when the failure of politicians to listen tb the unilateralist argument might easily have blown the world to pieces.

Because I am one of Foot's admirers - and envious of the elegant clarity with which Dr Strangelove, I Presume is written - I have struggled to find points at which our political judgements on strategy meet. The best I have managed is the contention that 'unilateral renunciation of the British H-bombs would not have had any measurable effect upon the balance of power'. That is not altogether different from my view that Britain should never have entered the nuclear race: we should have remained a contented, but junior, partner in an alliance which depended on the American deterrent.

However, a sensible decision not to acquire nuclear weaponry is quite different from an announcement that it is to be abandoned - particularly if the new policy is decided unilaterally. For Britain to have given up its far from independent missiles would have sent a series of dangerous signals to