No one today under the age of 40 can have much direct memory of the figure who - next to Aneurin Bevan - was the most exciting Labour politician of the 20th century. Anthony Crosland died in February 1977, at the age of 58, from a stroke while still en poste as foreign secretary.

Yet his claim to fame has never rested on his periods in high government office or, indeed, on his prospects of rising to the top of the Labour Party. (In 1976 he unwisely stood against James Callaghan to become party leader and prime minister, collecting a mere 17 votes, 20 fewer than Tony Benn.) What many would argue singled him out from his more routine colleagues was his contribution as a socialist theoretician. Without belittling his seminal, if dated, The Future of Socialism (1956), I have never found it easy to accept that this provides the entire explanation for his remarkable and enduring appeal. That has always seemed to me to rest instead on a curious, swashbuckling quality he possessed - combining intellect, glamour and arrogance in roughly equal proportions - which until then had seemed to be the exclusive prerogative of the more engaging sort of Tory.

Even to say that runs the risk of making him sound like some sort of preincarnation of Alan Clark - and Crosland was always much more considerable than that. But, at the same time, it would be foolish to deny that the raffish side of his character - what Dick Crossman, of all people, once called his "bohemian flippancy" - formed part of the charm that he always held, particularly for the young. In a markedly prim and prissy period of left-wing politics, he filled the romantic vacuum.

It was the great merit of Susan Crosland's unorthodox biographical study of her husband (published within five years of his death) that she brought this out and, by concentrating on his personal rather than public life, fully developed it. This much more conventional political biography has few such insights to offer but, in a consistently balanced and readable way, fills in some of the gaps that his widow left. Less concerned with Crosland's ideology and writings than David Reisman's twin (predominantly academic) volumes published two years ago, it nevertheless supplies a workmanlike account of its subject's political career.

That career, it has to be said, was in the last resort a disappointment. It started out under Hugh Gaitskell, with a promise that was never quite fulfilled. There was a reason for that. Crosland was, above all, the disciple whom Gaitskell loved - and it was this feeling of near-homosexual affection for him on the part of his leader that gave him his jump-start over most of his contemporaries. It was also the reason why a March 1960 NS profile, suggestively entitled "Mr Gaitskell's Ganymede", caused the enormous offence that it did. But Gaitskell was not, in fact, the first senior Labour politician to feel that sort of attraction towards the dashing, debonair figure that Crosland represented. The much more openly homoerotic Hugh Dalton drooled over him from the moment he first set eyes on him at Oxford just after the war.

Did Crosland reciprocate any of these feelings? To his credit, Kevin Jefferys is remarkably candid about this aspect of his subject's lifestyle, writing forthrightly of his having been, as an Oxford undergraduate and legendary young Trinity don, "almost certainly bisexual". Later on, this phase was firmly put behind him. In the late 1950s I can recall going more than once to his bachelor flat in the Boltons and being struck - I hope without too much youthful prurience - by the evidence of lipstick-stained glasses and red cigarette butts that always seemed to litter the place.

To the end, he remained conscious of his good looks - which is presumably why (though he always drew the line at wearing "tails") he took far more trouble over his clothes than did most Labour politicians of his era. If he thought Labour, he dressed Tory, usually in a dark, well-cut suit with a striking coloured shirt complete with French cuffs. No doubt that helps to explain why the Conservatives resented him as much as they did.

They had another reason for doing so. He was the first fully paid-up Labour "revisionist", long before the coming of Tony Blair. The cleverer among them spotted the threat that this could constitute to their hegemony. But Crosland, a clumsy tactician, never had the chance of imposing his views on the party.

His rivalry with Roy Jenkins - originating when Jenkins became chancellor in November 1967 - scuppered whatever slight opportunity there might have been of a Gaitskellite inheritance, even in the 1970s. Doubtless there were faults on both sides, but in the light of the dispassionate account offered here of their relationship, it is difficult not to conclude that it was Jenkins who was normally the aggressor. That did not, however, stop him from writing in his own memoirs, A Life at the Centre (1991), that Crosland was "the most exciting friend" he had ever had. In its own more modest way, this lucid but never florid biography helps to explain for a new generation why that should have been so.

Anthony Howard was editor of the "New Statesman", 1972-78