John Rentoul: Why did a young Tony Blair say he found Marx 'illuminating'? In order to survive

The truth is more interesting than the myth. The point about the young Tony Blair is not that he was influenced by Marx, but that he rejected Marxism. Oh, how they laughed, on the Today programme and at The Daily Telegraph, at Blair's writing to Michael Foot in 1982 that he found Marx "illuminating in so many ways". What a joyous embarrassment to think the Prime Minister was a naive lefty once. And how they cried, on the left, for the early promise of romantic "radicalism" so cruelly betrayed.

Chief among the tearful tendency was Robert Taylor, the distinguished former labour editor of the Financial Times who found the biographical gem in papers donated by Foot to the People's History Museum in Manchester. In his commentary in the New Statesman, Taylor (who left Labour to join the Liberal Democrats three years ago) mourns: "It is his personal tragedy, as well as the tragedy of the Labour Party, that the ambitious idealist was transformed into an authoritarian and hubristic machine that destroyed the ethical values of a Labour movement he once claimed to hold so dear."

Wrong, wrong, wrong. Even as I congratulate and envy Taylor for his find, I must take issue with his interpretation. The key to understanding Blair's handwritten letter is to remember that 1982 was a very, very long time ago. Then, nearly every youngish person in the Labour Party was either a Marxist or felt obliged to acknowledge an intellectual debt to Marxism - especially if they had pretensions to being an intellectual themselves. As Blair said in his letter: "It is impossible to understand the 30-40 age group in today's Labour Party" - he was 29 - "without understanding the pervasiveness of Marxist teaching."

But what is striking about Blair is that he never had any time for it. When Marxism Today had just begun to redefine Marxism out of existence, Blair was an anti-Marxist. He did not put it like that: his natural tact and instinct for survival meant that he paid ritual observance to the Labour Party's household gods. He even says in his letter to Foot, "I came to socialism through Marxism" - an unlikely sentence, especially from someone who said his politics were the other side of his Christian faith. But he immediately qualified it: "To be more specific, through Deutscher's biography of Trotsky." Which is, of course, the story of how Marxism in practice betrayed the humanitarian ideals for which it claimed to stand.

He told Foot: "I actually did trouble to read Marx first hand", although he does not say what. Probably The 18th Brumaire and The Communist Manifesto, like the rest of us. But the only thing he says in his letter to Foot about Marxism as an ideology is that he found it "stifling" because it becomes "an excuse to stop searching for the truth". He would not have needed to say more to Foot, possibly the greatest authority on the history of British socialism.

However, as Blair's biographer, I have the 23-page typescript of the essay he wrote three months later in which he set out his views more fully. It was written in about October 1982 for an Australian political journal, but never published. "The left must look for its political philosophy to something more sensitive, more visionary, in a word more modern, than Marxism," he wrote. "The irony lies in the homage paid to Marx at a time when most casual political observers and certainly most voters hold him and the regimes founded on his political philosophy in fear and distrust. The major political change since the 1930s, for Europeans, is the existence of the Eastern bloc of Europe. It is impossible to underestimate the influence which this has had on the thinking of the post-war generation. It has destroyed faith in Marxism as a liberating force and is a remorseless deterrent to experimenting with such a philosophy here. It is quite vain for Marxists to offer explanations for repression in Marxist states, no matter how plausible they are. People will not risk it." It is a curious argument, typical of early Blair, in which the rightness or wrongness of the Marxist analysis is irrelevant. The voters will not wear it, so forget it. It would be "political suicide", he wrote.

His political formation was, thus, not like that of many of his co-conspirators in the making of New Labour. Peter Mandelson, John Reid, Alan Milburn and Jonathan Powell, Blair's chief of staff, were Marxists of varying rainbow stripes in their youth. Blair was never tempted by the certainties of that world-view. What is more, despite the gushing of the need for a "mammoth" reconstruction to save the country from Mrs Thatcher's "economic madness" (the Foot letter) or the "massive reconstruction of industry" (the Australian article), he was never even a leftwinger in internal party politics.

Part of the thrill at the BBC, The Daily Telegraph and the New Statesman is prompted by Blair's "admiration" for Tony Benn 24 years ago. This is based on one sentence that reads: "T Benn is in one sense quite right in saying that the right wing of the party is politically bankrupt." It is a bit like saying someone is a Nazi if they write: "A Hitler was in one sense quite right in saying that the tank has transformed military tactics." In saying that the traditional Labour right was bankrupt, Blair was no more than regretfully describing what Marxists call the "objective reality".

That Blair could not bring himself to use Benn's first name is a clue to his true feelings. In fact, Blair and Foot had been co-conspirators against Benn at the Beaconsfield by-election, which Blair fought and lost in May 1982. Foot was asked on television what he thought of the failure of the organisers to invite Benn to campaign on Blair's behalf. "I think they've exercised their discretion very well," he smiled. Later in the letter Blair urges Foot to "go on the attack" against Benn for his refusal to condemn the "quite horrendous practices of TB's ultra supporters" (a phrase that means something different now) in the 1981 deputy leadership election.

The mistake with Blair has always been to think that he is typical - of anything. He was always the exception rather than the rule. As a young man he mixed with people who took drugs, but he didn't take them. He was confirmed in the Church of England - even more unfashionable in 1974 than being right-wing Labour.

In politics, the truth as opposed to the myth of Tony Blair is that he has been unusually consistent. He has always advocated a ruthless electoral pragmatism in pursuit of mild social justice. And he has always confused people with his "radical" rhetorical flourishes.