Mr John Major is fortunate that his interpretation of the Conservative party's recent history hangs together. Otherwise his intervention in his party's leadership contest, would justify his critics' claim that it is the peevish cry of a half-remembered man, begging for his place in history. Certainly, that is how Baroness Thatcher and her friends - all supporting Mr Iain Duncan Smith - will view it.
Not even Baroness Thatcher can gripe about Mr Major's decision to speak out for Mr Kenneth Clarke. His choice rings true. Lord Heseltine aside, Mr Clarke would have been the chosen successor had Mr Major fallen from office before 1997. He retained Mr Major's sympathy during the wilderness years of Mr William Hague, though they spoke rarely; kindred spirits, not close friends.
So passionate was his denunciation on Wednesday of Baroness Thatcher that he spurned the chance to praise Mr Clarke, other than to confirm the bare fact of his support. Twice Mr Major told his interviewer that he did not wish to talk about the past - by which he means Baroness Thatcher - before doing so. This will not have helped Mr Clarke as much as a polite lie about her status as a past heroine would have, but his fury got the better of him.
Mr Major constructs a rational case to explain this. He argues that in 1990 he inherited a ruinous economy, a wrecked European policy and an unworkable and unpopular system of local taxation. Into the bargain, he had to fight the Gulf war. Out of this he built economic strength, a surprise election win and six years of able centre-right rule.
He also had to face the hard-headed, relentlessly plotting Eurosceptic right that encircled Baroness Thatcher. After the 1992 election Baroness Thatcher did summon young MPs to her rooms to tell them that voting treacherously against the Tory whips over Maastricht was more honourable than voting against their nation's sovereignty.
Mr Major does not blame the right alone for the calamity that overcame his government. But he believes it played directly into the opposition's hands. New Labour grew from Conservative weakness as much as it did from the Chancellor Mr Gordon Brown and Prime Minister Mr Tony Blair's strengths. A harder man might have acted against it. Mr Major could only watch in horror.
And that horror is at the root of everything between him and Baroness Thatcher.
For though Mr Major can clutch at the very good grounds for his dislike of Mr Duncan Smith and the very good grounds for his support of Mr Clarke, what it is really all about is psychology. "I was not smiling," he once remarked when why so many photographs show him grinning beside the woman he later criticised. "I was baring my teeth." Were the facts of the case against him, as they are not, were the Eurosceptics unanswerably right and Mr Hague now in Downing Street on the back of his "save the pound" campaign, Mr Major could still not be reconciled to Baroness Thatcher. He finds her physical presence troubling; she shaped too much of his past.
It is overlooked now, but Baroness Thatcher was evicted by her party because she was too anti-European and, over the poll tax, too extreme. Mr Major was the welcome middle ground replacement and, in office, behaved as such.
As his party chooses its fourth leader in just over a decade, Mr Major has rightly decided not to hesitate again. He has talked about the past not just because he is rooted in it and it troubles him endlessly, but because more than any Conservative he understands the destructive acid that for a decade has seeped from under the door of Baroness Thatcher's Belgravia house, corroding his premiership, Mr Hague's leadership and resulting now in the poisoned candidacy of Mr Duncan Smith. He knows that unless the acid is stopped the consequences are clear. Mr Major is aware that he might turn out to have been the last ever Conservative prime minister.
Julian Glover was Mr Major's assistant in the writing of his autobiography.