Just like one of those iris shots beloved of the makers of silent films, let's start by focusing our attention on a single detail, a plaque on a wall: Rue Jean Cocteau. Slowly the iris expands until it coincides with our entire field of vision. The image, now of a dusty, dozy village square in northern France, encompasses a large covered market, a car park, a cluster of shops (one of which, a men's clothing store, specialises in Jean Cocteau ties, T-shirts and cuff links) and, a little way off from the centre but situated precisely on the above-mentioned rue Jean Cocteau, the gaudily canopied Cafe Orphee. Further off, at the end of that same street where it forks to the left and right, is a tiny, squat Romanesque church: the Chapelle de St Blaise des Simples, inside which Cocteau lies buried. The village in question, in the former departement of Seine-et-Oise near the Fontainebleau forest, about 56 kilometres from Paris, 45 minutes by car on the autoroute du Sud, is Milly-la-Foret.
If one strolls down the rue Jean Cocteau, one eventually arrives at St Blaise des Simples, described by Cocteau, in an illustrated album published in 1960, as resembling "a poor hag hunkered down [presumably to urinate] at the edge of the road". Once a lepers' chapel, it is, to be sure, a fairly unlovely edifice. Inside, though, it has been decorated - or, to use his own preferred word, "tattooed" - by Cocteau. Directly above the primitive altar is a head of Christ, flanked by the profiles of two conspicuously virile angels. Over these figures, just below the roof's exposed wooden beams, another, now freshly resurrected redeemer is surrounded by a trio of Roman centurions in mini-togas, one of them yawning, the other two fast asleep. There's also a naked young angel, muscular and completely bald. And on the floor beneath our feet is the poet's oblong tombstone.
It's a simple slab of stone. Cocteau's name, like a letterhead, is inscribed at the top, and on the lower right-hand side, scrawled in his familiar spidery handwriting, are the words "Je reste avec vous" - or, in English, the Ozymandias-like "I am still among you".
But is he still among us? Has he, like all great artists, survived his own life? Or, instead of an artist's true posterity, has he had what might be called an "imposterity"? Does he impinge on our current consciousness as nothing but a dandified dilettante adulated by the literati, glitterati and twitterati of his own era but utterly irrelevant to ours? Cocteau wrote poetry, fiction, drama and criticism; he directed several celebrated films; he produced thousands of sketches and paintings; he collaborated with such musicians as Stravinsky, Satie, Milhaud, Poulenc, Honegger, Henze and Menotti; he acted on both stage and screen; he travelled around the world in 80 days (long before S J Perelman, Nicholas Coleridge and Michael Palin); he personally trained the washed-up Panamanian prizefighter Al Brown so effectively that Brown regained his world bantamweight title; and he played the drums in a couple of Parisian nightclubs. Was he a maestro of every conceivable art form and an authentic master of none? Was he, in short, no more than the effeminate, opium-smoking poetaster of popular legend?
What I would venture to propose, rather, even to those who have scant affinity with the exacerbated aestheticism of his sensibility (Cocteau reiterated the term "poet" as often and obsessively as a navvy would use another sort of four-letter word), is that he was actually one of the most significant artists of the 20th century. The influence of his writing, both poetry and prose, is detectable in the work of figures as various as Radiguet and Genet, Edith Sitwell and Mishima; that of his film-making in the productions of the New Wave - Truffaut, Godard, Demy, Resnais, Varda and company - as well as in those of Bresson, Melville, Pasolini, Visconti, Bertolucci, Franju, Bergman, Anger, Fassbinder, Ruiz, Carax, Almodovar, Greenaway, Jarman and Tim Burton; and even that of his essential posture in the behavioural mannerisms and sartorial style of countless young French acolytes to this day as equally, if more obliquely, in the white-clown dandyism of someone like Andy Warhol.
In a career that spanned nearly six decades, Cocteau met everybody and did everything (albeit an "everybody" and "everything" as exclusive as they are inclusive). Yet he was also, by virtually universal consensus, a profoundly tormented man - the German novelist and diarist Ernst Junger, who saw a lot of him during the occupation years, referred to him as a "man in hell" but one who "had made himself comfortable there" - and that torment can be traced to two fundamental dramas in his life with which he never properly engaged in his work.
The first of these was his homosexuality. It was no secret. Yet Cocteau never put his name to an openly, unashamedly homosexual text and invariably alluded to his male lovers - the most celebrated being the precocious novelist Raymond Radiguet and the actor Jean Marais - as his "adopted sons". Even in his private diaries, which he always intended to be published posthumously, he couldn't bring himself to confront the truth of his relationships with them, as though he genuinely hoped to cheat posterity - to cheat God.
Cocteau's father committed suicide, in murky circumstances, when he was an infant, and it is probably the case that he grew up believing him to have been secretly homosexual. Certainly, his own oeuvre is open to interpretation as an encoded allegory of homosexuality, encoded by the self-censorship without which he would have been incapable of creation (the Beast in La Belle et la Bete, the theme of incest in both Les Enfants terribles and Les Parents terribles, the enduring fascination with the Oedipal archetype). Until recently, however, it was all but impossible to explore this aspect of Cocteau's life, given how defensive his "set" remained about his sexuality, and none of his earliest biographers ever properly addressed the question. With the publication of Marais's extremely candid memoirs, and also his correspondence with his lover, the situation altered significantly. Marais even made public the quatrains, of a quite breathtaking obscenity, that Cocteau would leave beneath the pillow of the bed they shared for 20 years.
The second drama relates to Cocteau's conduct during the Second World War. Although, once more, it's hardly news that he was no resistant, the precise nature and extent of his "flirtation"with the Nazi cause - or, to be more exact, the French collaborationist cause - was for many years left discreetly unelucidated. But in 1989, the centenary of Cocteau's birth, Gallimard published the 700-page-long, day-to-day diary he kept from 1942 to 1945. This volume is an astounding document, not just of a period but of a mindset, detailing as it does Cocteau's admiration for Hitler and his belief - shared by most members of his entourage - that the Fuhrer ought to be permitted "to pursue his fantasy to its ultimate conclusion". In the diary's latter pages, not surprisingly, he begins to change tack. But in spite of the difficulties he faced during the liberation, along with the unrelenting innuendoes of left-wing critics, he neither destroyed nor revised that diary, insisting it be brought out posthumously as it stood.
Such indiscretions might have sunk a lesser figure. Cocteau's novels, however, have never been out of print; his films, most of which can now be purchased on video and DVD, are widely acknowledged as classics or near-classics; his best plays continue to be staged, not just in France; and, not least, his pouty Orpheus profile - as instantly identifiable a logo of his achievement as Mickey Mouse is of Disney's - is as ubiquitous as it ever was. Yet there is something about Cocteau that has always set British teeth on edge, and it may be that it's his very versatility - not to mention his ineradicable glamour - that continues to mediate against his elevation to the status of a classic.
"Jean Cocteau: the naked dandy" is at the National Film Theatre, London SE1 (020 7928 3232) throughout March
Gilbert Adair's new novel, Buenas Noches, Buenos Aires, is published by Faber & Faber