Geoffrey Wheatcroft: He did do God. And that, in the end, is what did for him

One curiosity of our political history is that only a minority of British prime ministers over the past century were brought up in the Church of England; another is that only a minority were Christians, in the sense of having any serious personal religion. The believers did not include Winston Churchill, for example, that characteristic Victorian agnostic.

Even the faithful didn't parade their faith in what is by most standards a faithless land. "We don't do God," Alastair Campbell famously said, and most premiers would have agreed. Although Harold Macmillan was a pious High Church man in private life, even he thought that if people wanted moral guidance they should get it from bishops and not politicians.

Which makes Tony Blair's open display of religious faith all the more striking. It explains why he is such an oddity in our public life; and perhaps why he has done the things he has done, for good or ill, and the means by which he has done them.

He has never been at all easy to categorise politically, at least in our domestic terms. He is obviously no socialist, radical or liberal, and as James Callaghan said after they had met: "I don't know what that young man is, but he isn't Labour." But nor is he a Tory. Blair is quite devoid of the reverence for history and custom which is (or used to be) a defining Tory characteristic. And his war in Iraq, among other things, has shown that he is likewise devoid of the Tory qualities of pragmatism and sceptical common sense.

In some ways he is more innately American than British. Blair may not have prayed with the born-again George Bush, but their shared faith was certainly a bond, and his wearing his faith on his sleeve would not seem too odd or embarrassing in the US, where more than half the population goes to church and where supposedly grown-up politicians can say they approach difficult problems by asking: "What would Jesus do?" It is very different here, where barely 7 per cent of us go to church regularly (and under 2 per cent to services of the Church of England). Again, he has been shrewdly described as a Christian Democrat, and he does fit into that continental European pattern, certainly more than the rival tradition of Social Democracy.

If most British people accepted Blair's religion as a kind of foible, they didn't give it much thought. Had they done so, they might have understood him better. Again and again, Blair has spoken in terms of conviction and belief. "I only know what I believe"; it was "the right thing to do". In his exalted valedictory address on Thursday, he said: "I did so out of belief" (that is to say, his decision to "stand shoulder to shoulder" with the US, which in his bizarrely ignorant way he believes to be "our oldest ally"). Or again: "But I believe one thing if nothing else - I did what I thought was right for our country."

And yet this sense of righteousness - some would say self-righteousness - has had some very strange consequences. At the very beginning of his premiership, Blair said: "I would never do anything to harm the country or anything improper. I never have. I think people who have dealt with me think I'm a pretty straight sort of guy."

In case anyone has forgotten the context, he was explaining away the fact that after New Labour had accepted a large sum of money from Bernie Ecclestone, the motor-racing impresario, the new government had waived the rules against tobacco sponsorship of sport. To anyone but Blair himself, it seemed a good deal more improper than "straight".

Since then, we have repeatedly seen the same thing. Blair's language is fervent or even messianic. He is St Paul: "The just shall live by faith." He is Luther: "Here I stand. I can do no other." And therein lies the problem. In the 1870s, Bismarck waged the Kulturkampf, his campaign against the Catholic Church in Germany and the Centre Party, the Catholic confessional party, and he was repeatedly outplayed by them. But then, as AJP Taylor puts it, even the ruthless Bismarck "could not rival the freedom from the principles and the scruples of this world which is given by devotion to a supernatural cause".

That fits Tony Blair exactly. His own devotion to a supernatural cause is sincere and deep; and he has continually displayed a quite remarkable freedom from the principles and scruples of this world.

In a half-ironic, more-in-sorrow turn of phrase, Roy Jenkins said that his young friend was "a little too Manichean ... seeing things in stark terms of good and evil, black and white". But Blair is not just Manichean; he is antinomian. He believes that "to the pure all things are pure" and that if you are of the elect you can do anything at all still in the certainty of salvation.

That is why, convinced New Labour was the party of virtue, he was happy to take money from any dodgy businessman around; that is why he, a dutiful Christian husband and loving father, sees nothing wrong in entertaining a pornographer such as Richard Desmond.

Above all, having persuaded himself that the Iraq war was "the right thing to do", he then resorted to utterly dishonest and deceitful means to persuade Parliament and the country that the war was necessary. His parliamentary speech in March 2003 is still admired by some. And he might almost have been preaching on Romans, chapter 3, verse 8: "Let us do evil, that good may come."

Even now, he cannot repent the way he justified the war in a manner that plenty of us guessed, and all now know, was simply false. He did not make a mistake in good faith, as his faltering defenders still claim. He said what he had every reason to know was, in all likelihood, untrue. But it was the right thing to do.

The question remains how this improbable God-botherer, this zealot, or even fanatic, ever came to govern our damp and torpid little island. Gordon Brown reminded us on Friday that his father was a Presbyterian minister, who taught him the importance of integrity and decency. But Brown does not seem to be a devout churchgoer, and not everyone will mind that so much as we ask ourselves whether we ever want to have a Prime Minister who is sure that he is always right because the Almighty tells him so.

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