Let's not mock Tony. After all, how many prime ministers have been sane?

Is our Prime Minister now as mad as a March hare? Has the undoubted pressure of high office driven him quite doolally, to the extent that powerful drugs or some form of therapy involving the use of electricity is regularly required to enable him to appear safely in public?

It hadn't really occurred to me that this might be the case, but it has most certainly occurred to Clam Short. Now Clare, you might argue, may herself one day become acquainted with the kindly nurse, the padded room and the straitjacket. But this surely does not diminish her ability to detect incipient madness in others. Here's what she told Michael White of the Guardian the morning after her blunderbuss of a resignation statement: 'There used to be a saying of the Tory whips when they were in power — this is the Tory whips, not me — [that] no one ever comes out of No. 10 completely sane.' Clare then paused and added that Jim Callaghan was the exception; he just 'carried on being Jim'.

On the radio this was described as a 'veiled' reference to the Prime Minister's mental health. I must say that, as veils go, this is a good way short of the full burka. It might be better described, in fact, as an 'unveiled' reference to the Prime Minister's mental health.

And what an enticing picture of No. 10 it conjures in one's mind: aides and apparatchiks feverishly working to disguise Tony Blair's rampant and consuming dementia Perhaps, as with King George III, Tony has an assistant who, each morning, examines the prime ministerial stools in the hope of discerning a cause of, or a cure for, his lunacy.

Clare's implied argument, such as it is, would seem to be that prolonged exposure to the job of prime minister induces a form of paranoia which later develops into full-blown, carpet-biting madness. It is a side-effect of that infamous bunker mentality which seems to establish itself within a few years of ascending to office. The gradual erosion of Cabinet government and the introduction of a quasi-presidential regime, which Ms Short details at some length, is the by-product of such a mentality. What develops is a mistrust and even terror, first of the media and later of one's own Cabinet and party colleagues, and then, finally, disastrously, of the electorate. In two speeches recently—the first regarding the decision to invade Iraq, the second the announcement to postpone the elections to the Northern Ireland Assembly — the Prime Minister has insisted that he is taking difficult decisions which, in effect, almost nobody else agrees with. But they are the right decisions anyway, whatever you lot might think. This sense of separation and distance might well be what Clare is driving at. But does it constitute lunacy?

If it does, then you might argue that the present Prime Minister is in the very best of company. There seems to be a direct correlation between such 'insanity' and truly effective premierships. Margaret Thatcher was referred to, not without some justification, as a mad old bat well before the rather shabby coup which summarily disposed of her. That same insularity and an apparently diminishing sense of selfawareness gripped hold of her some time after the 1987 election. As soon as she started referring to herself as 'we', you knew it was time for the screens.

Churchill's decline was, perhaps, more a result of age and infirmity than the pressure of office, but it was present, in those final years, nonetheless. Harold Macmillan was similarly afflicted in his dotage.

The exception to the rule is Clement Attlee. Lord Healey was a backbencher in that first postwar Labour government and remembers a man most notable for his utter normality and rather crushing sanity. 'And in Attlee's case, he was actually improved by being prime minister,' he told me. 'He left office a better man — more confident in his ability to make judgments and take decisions.'

Perhaps Denis's own judgment has been clouded by the passage of time, however, because he also insisted that Hugh Gaitskell was an entirely normal individual. I'm not convinced. Telling the electorate that one should avoid washing and that not washing can improve the health strikes me as being at the least a little on the eccentric side.

Alec Douglas-Home was slightly mad before he became prime minister and seems to have left office somewhat improved. Peking, Alec — Peking, Peking, Peking, Peking, Peking, Peking,' his wife Elizabeth would constantly repeat to him as he walked down the steps of an aeroplane, while he was foreign secretary. This was to prevent him addressing his hosts with the words, 'I am delighted to be back in Montreal.'

Ramsay MacDonald, meanwhile, should have been sectioned in about 1931. He began to suffer chronic insomnia and delusions. He could be seen, while making a speech in the House, looking nervously over his shoulder, convinced that someone was about to shoot him, and once lost consciousness entirely during an address to a disarmament conference in Geneva. I suppose the lesson here is that while the greatest prime ministers may have had a touch of madness, not evety incumbent with a touch of madness has necessarily been a great prime minister.

I rang up Sir Edward Heath to ask him if he was mad or had been rendered mad by high office. This was, I think you'll agree, a ticklish assignment. My own view is that Sir Edward left Downing Street with his sanity entirely intact — a view with which, not unsurprisingly, he entirely concurred. 'The thing is, I had a huge breadth of outside interests, which I maintained while in office. There was music, and later there was sailing. And I continued to do these things, even while being prime minister.' He may have a point here.

John Major endured what was perhaps the most difficult and unpleasant premiership of the last 50 years, and left office with remarkable dignity and sanity, given the fact that in his case a certain paranoia about colleagues would have been evidence of an entirely rational state of mind. Strangely, I was once required, while working for the BBC at a sununit meeting in Essen, to peer in his left ear which, he complained, contained some kind of blockage. I peered in the left and Chris Meyer, then his chief of staff, peered in the right. We didn't see anything.

This was a surreal experience, but not one which betokens madness, I think; still less, his reported fondness for frozen cheese, peas and Edwina Currie. These are just peccadilloes, don't you think?

Perhaps Lord Healey is right. 'Journalists are far more likely to be afflicted with delusions and paranoia than politicians,' he said, dismissing any notion that Tony Blair should be escorted to the booby-hatch post-haste. 'It's just the usual thing,' he said of Clare Short. 'Diminish your political opponent by suggesting he's mad.'

Well, yeah, maybe. Sure. It's rather good fun to speculate, though, isn't it?