Tony Blair is right: A Journey is not a routine political autobiography. Naturally, it was written in the hope, in part, of rehabilitating the author's reputation. Yet the moral certainty that bursts out of every page makes it more than the usual attempt to justify the unjustifiable. It is a testament from a man who believes that once they understand his motives and methods, his detractors will see the error of their ways and come late to repentance.
The messianic tone is confirmed and intensified by the occasional admission of guilt. Blair attributes virtually all his acknowledged mistakes to failure to implement his own ideas with the speed and to the extent that their merits justified. No one reading A Journey could believe that its advance and royalties were donated to the Royal British Legion in order to salve a troubled conscience. Blair believes that he was right to invade Iraq in 2003 with the absolute certainty that is simultaneously his political strength and his intellectual weakness.
The strength of conviction is not matched by clarity of expression. Blair writes that he "can't regret the decision to go to war". That is clear enough, but he extends the assertion with pure gobbledegook:
I can say that I never did guess the nightmare that unfolded and that too is part of the responsibility. But the notion of responsibility indicates not a burden to discharge but a burden that continues. Regret can seem bound to the past. Responsibility has its present and future tense.
Whatever that means, he goes on to explain the necessity to topple Saddam Hussein with an argument that is undeniably intelligible. It amounts to an inventory of slaughter - on one side of the balance sheet, the Iraqis who died during, and in consequence of, the war and, on the other side, the killings of which Saddam was guilty. Naturally, he chooses the figures most favourable to his argument. The Lancet estimate that the war was responsible for 600,000 deaths (and only up to 2004, though the book does not say so) is brushed aside. But the dubious use of statistics is less revealing than the belief that the table of relative attrition is some sort of vindication of a war which, we were told, was fought to rid the world of Saddam's weapons of mass destruction.
Strangely, the account of a journey that made a diversion through Rome never mentions the Roman Catholic Church. Blair, however, is wise not to measure his decision to invade Iraq against the papal definition of a just war. Just wars must have the prospect of a successful outcome. The best he can offer by way of an assurance of success is the repetition of Zhou Enlai's judgement on the significance of the French Revolution: "It is too early to say." But one thing is clear: whether the call to battle came from God or from George W Bush, Blair answered without the slightest doubt about the justice of the cause and with little regard for either his personal popularity or his electoral prospects - the two considerations that his more simplistic critics claim are his principal preoccupation. A Journey dispels the myth that Blair had no strong beliefs. On the contrary, his weakness was too little doubt.
From the moment he became Labour leader, Blair was determined to re-create the party in his image - eager to alleviate suffering and reduce injustice, but wholly opposed to making any fundamental change in the way society is arranged. And he was convinced that he, as well as those around him, could transform his decent instinct into a new theory of government.
Even now, Blair maintains total confidence in the ragbag of ideas that was the New Labour prescription. His faith in the market remains absolute and he dismisses the banks' collapse as "the failure of one sector", not an inherent weakness in the system of "light-touch regulation". He also argues in favour of direct taxes being held at "a competitive" rate while the necessary revenue is raised by an increase in VAT. Gordon Brown's decision to "ditch" the Manchester super-casino - the quick fix to the city's unemployment problem - was "a real shame". All these notions are advanced as if men and women of sound judgement and good intentions accept them as self-evident truths. Yet he admits that, by the end of his premiership, only John Reid and Tessa Jowell were still true believers. If that does not shake his faith in the Third Way, nothing will.
Ideological discussion bores him and he confuses principle with prejudice. That is why, at first, the ideas that guided his domestic policies seemed to be united by only one common theme - their popularity among the "target voters" who secured him three consecutive election victories. That objective was, I wrongly believed, what determined his reaction to the furore which followed the discovery that Harriet Harman had sent her son to a grammar school far outside the catchment area in which the family lived.
His first impulse, he tells us, was to sympathise - one parent to another - with Harman's determination to do the best for her child. Then he moved on to what he still regards as the overriding reason for the Labour Party not making public the anger that so many of its members (including most of Blair's aides) felt. "Before we know where we are, we've really unsettled sensible middle-class opinion." That policy criterion is not as cynical as it first sounds. Blair's Summa Theologica was, and no doubt still is, built around the importance of following sensible, middle-class opinion. Compared to the war in Iraq, the "Harman affair" was a little local difficulty, but it revealed Blair's true system of values.
It was the discovery of how Blair had responded to that imbroglio which convinced me he was not the party leader I'd hoped for, but I should have realised my mistake much earlier. During his early years in parliament, we saw a great deal of each other. His first front-bench job was as the junior member of the opposition's Treasury team when I was shadow chancellor. When he was promoted to Labour's "City spokesman", he occasionally asked my opinion on small items of policy and performance.
On 13 June 1988, we talked about how he should respond to a government statement on an inquiry into the collapse of Barlow Clowes, a Gibraltar-based investment company which, despite a Department of Trade certificate of viability, had gone into liquidation. His response seemed fine to me, but I made the mistake of saying that I felt very little sympathy for the men and women who had lost their money; they had invested their savings "offshore" in order to avoid paying tax. Blair reacted with polite outrage. The victims were, he said, honest citizens doing their best for their families and he proposed to speak up for their laudable thrift. He had not even considered that people can, while acting within the law, betray their obligations to society.
The Barlow Clowes revelation did not prevent me from supporting Blair's candidature for the Labour leadership enthusiastically. He telephoned me on the Sunday after John Smith died and I told him he had my vote. He said - I believed him then and I believe him now - that although he had made up his mind, he was unhappy about pushing Brown aside: "Gordon has always wanted it much more than I do and wanted it for so long." In those days, Brown and Blair were David and Jonathan rather than Cain and Abel, and Brown was the senior partner in the relationship. During Neil Kinnock's leadership Blair came to see me, distraught at the Tribune Group's decision to include Brown, but not him, in its "slate" of recommended shadow cabinet candidates. He stood, nevertheless, and was elected. And even in the anguish of rejection by the Tribune Group, he still exhibited both admiration and affection for Brown. Yet A Journey is a sustained assault on his old friend's conduct and character.
The only plausible explanation for this is bitterness - bitterness about attempts to make him keep his promise to abdicate in 2002, bitterness at being deposed before he was ready to go and, most of all, bitterness about the obstruction of his most cherished policies. The index entry for Brown is a litany of objections, most of them to proposals that a wholeheartedly left-wing government would not have even contemplated: "Against Millennium Dome . . . Resists tuition fees . . . Opposes academies school programme . . ."
Blair could not be more frank in explaining why he remained so long and was so sure that his departure would end in disaster: "Only through holding to the New Labour course, with passionate not tactical engagement, could we hope to succeed. . . . But I'm afraid [Brown] couldn't see it."To reject New Labour was to reject Blair himself - not the leader of a political party, but a one-man crusade on a personal mission to make the world fit for the sensible middle classes to inhabit.
Though it is possible to explain why the book casts Brown as villain, parts of A Journey are simply inexplicable. What purports to be a serious account of political reform and international statesmanship is interrupted from time to time with accounts of the Blairs' physical relationship. The public comments on what should remain private matters are written in the style of cheap romantic fiction and it is so embarrassing to read them that their inclusion in the book raises grave questions about the author's judgement. Yet there are also parts of the book that remind the reader why he rose so high so quickly.
In February 2007, he "explained [to Brown] that there were only two ways that Labour could win the election. One was a decisive rupture with [his] time in office . . . That would require a new and credible agenda . . . The other was 'Continuity New Labour'." He wanted his successor to choose the second option. I longed for him to choose the first, but Blair was right to say that making the choice was essential. Unfortunately, Brown chose neither course, and so the Labour government ended in tragic irony. Blair, who never wanted Brown to become prime minister, described the path to victory. And, by rejecting his advice, Brown convinced Blair that he had been right to hope for a different successor.
Back in 1988, when John Prescott challenged me for the deputy leadership of the Labour Party, Kinnock organised a campaign to persuade me to accept a second stint in a job that I never wanted. Brown and Blair were persuaded to convince me that it was my duty to accept the nomination. They came into my room straight from a Monday-night meeting of the Tribune Group and announced that a motion supporting my candidature had just been carried. We then enacted a version of an ancient political joke. What, I asked, like the dying MP whose constituents had voted on a message of condolence, was the result? Brown answered with the hackneyed punchline. "Ten in favour, seven against with six abstentions." But, Blair added, "most Tribune members will vote for you. Real ones, not just those of us who thought we had to join."
Morally speaking, Blair the charming zealot who was prime minister for ten years was a much better man than Blair the young MP on the make, who claimed to support unilateral nuclear disarmament, withdrawal from the European Union and the nationalisation of almost everything. But he was also much more dangerous. As things turned out, he became the embodiment of the dilemma that faces enthusiasts for conviction politics: what if the convictions lead to behaviour that more measured judgement would have rejected? The catastrophe of Tony Blair's premiership was that he came to believe that he was called by providence to depose Saddam Hussein. And the tragedy for him is that the Iraq war is the one thing for which he will be remembered.
Hutchinson, 718pp, £25
Roy Hattersley was deputy leader of the Labour Party from 1983-92. His biography of the Liberal prime minister "David Lloyd George: the Great Outsider" will be published by Little, Brown on 16 September (£25)