Gwyneth Paltrow's astonishing depiction of Sylvia Plath makes a new film of her life with Ted Hughes worth seeing, writes Eileen Battersby, admitting to previous ambivalence about the poet.

Ted and Sylvia, Sylvia and Ted. It's not a subject that overly appeals to me. Who wants to explore the battlefield of someone else's marriage? Hughes and Plath, two vastly different poets, is far more interesting a subject. But when a movie of a poet's life is entitled Sylvia, odds-on bets suggest it is going to be about the life and death, not the work.

Ted and Sylvia, Sylvia and Ted has spawned a voyeuristic industry split into two camps: the champions of Sylvia the wronged icon versus the defenders of Hughes the unlucky survivor of two suicide women.

In the tussle to lay the blame the poetry of both writers has often got lost. Who is the villain? Who is the victim? Both or neither? After all, both were supreme egoists. Is their story a tragedy or merely another human mess? Death separated the protagonists by 35 years, during which time Hughes kept his silence until the publication of Birthday Letters, mere months before his death, in 1998. Now they are both dead. Why not let the sleepers - one-time lovers, long-time rivals - rest in peace?

So duty rather than curiosity guided my steps to a preview of Sylvia, which features Gwyneth Paltrow as Sylvia Plath. Here we go again, into the often queasy world of the biopic. Ariel would have been a more substantial title.

As a neutral observer, albeit one drawn more to the physical, natural world of the best of Hughes's poetry than to the intensely pitched psychological and confessional drama of Plath's, I was taking no sides, although for me there has always been an ambivalence about Plath the poet and the iconic victimhood created by her suicide. I guess I still see her as more of a godless maverick than a victim. For all the dominance of life and death as themes in her work, she never refers to the spiritual, to God or to any god.

Much of the pre-release publicity has been dominated by those who knew the pair; 41 years after the freezing February day that the lonely, distressed Plath killed herself we are being subjected to how Al Alvarez, the former Observer poetry editor, critic and writer, and an intimate of Hughes, believes he could well have saved her. Ruth Fainlight, a US poet, also feels that, had she acted differently, Plath might have lived.

Perhaps they could have saved her, but they didn't. History cannot rewrite itself. And Plath's meticulously choreographed death, at 31, ensured that an interesting poet, comparable on some levels to the great Emily Dickinson, remains very interesting.

Plath's autocratic voice arrests because there was action beyond intent. Here was an often terrifyingly witty woman who nobody could save. Virginia Woolf had had a minder in the form of her concerned husband, Leonard, and although he helped he couldn't save Woolf.

Plath had no minder. The central difficulty and strength of Sylvia lie in the revelation of Paltrow's inspired multitoned portrayal of an explosively mercurial character who paid the price of hyperconsciousness and her history of manic depression. For Paltrow alone I'd say see it. As for the rest, I'd continue to say read Hughes, read Plath, particularly the Ariel collection and The Bell Jar.

Whereas Nicole Kidman, using a plastic nose and a studied series of twitches and long stares, impersonated Woolf in the appalling screen version of Michael Cunningham's novel The Hours, Paltrow brings an emotional intelligence, candour and lucid chaos to her interpretation of Plath that might well cause sceptics to gasp. She stalks Plath and frequently corners her in all her "strange glitter".

Daniel Craig, a good actor, falters in his pursuit of the messianic Hughes. Aside from lacking the height and sheer physical splendour of the poet, who even in old age, when I saw him, retained a dangerously sexual presence, Craig plays Hughes as bewildered escapee from the doomed Plath's emotional turbulence. Hughes was no lost soul. But then nor was he a completely ruthless philandering swine. He was a man no woman could hold, and therein lay Plath's definitive self-destructive challenge in a life littered with and ultimately ended by chronic self-destruction.

Plath is a tricky writer. It seems you are either too young to read her or suddenly too wary of the autobiography and the myths. But Paltrow appears to have absorbed the essence of The Bell Jar, Plath's disturbing, impressive and autobiographical only novel, as her route into the mind, emotions, black humour and relentless candour of the self-absorbed poet. No shrinking violet was Plath. She was tough, restless, ferociously ambitious and cerebral, possessed by desperate needs that developed into rampaging devils. Hughes was not far off the mark when he wrote, "Your writing was also your fear," in 'Apprehensions', from Birthday Letters.

No prizes are likely to target John Brownlow's workmanlike script, which has to field the impossible demands of recreating private conversations as well as the practical difficulties of being denied permission to quote from the work of Hughes. But Brownlow has closely read Birthday Letters, noting lines that contain volumes. As early as their first meeting, as depicted in the film, Plath sees Hughes at a party and approaches him. They dance, he notes the arrival of his date and Plath bites his cheek.

Had a man decided to mark his prey so openly there would be uproar. Plath was direct and clever, flattering his ego. From the first she drew blood, initially his and from then on her own, largely in the form of multiple humiliations induced by crazed jealousy and open terror of his leaving her. It would mean failure - and Plath did not like failing at anything.

There are a few light interludes. A fanciful though true scene - look to Birthday Letters - has the courting pair aboard a Cambridge punt. She stands, declaiming Chaucer to a herd of interested cows. A later, far darker sequence, also on water, shows the couple now married, he writing and her writer-blocked and baking mountains of cakes, in a rowing boat. This time it is not a calm river: it is the ocean. Suddenly the shore is gone. He realises the current has taken them out to sea. It is dangerous. She relaxes into her Lady Lazarus mode, recalling her previous suicide attempts. This is the point at which the symbolism of their impending disaster is at its clearest.

As a study of a real marriage, Sylvia is intrusively explicit. Based on life rather than art, it will likely make others feel uncomfortable with the intimacy enacted on screen. How must the Plath and Hughes children feel about seeing actors playing their parents, how will they confront the graphic intercourse?

Consider the scene in which Hughes returns, summoned by Plath. She, clearly prepared to seduce him, appears to have won. Naked, they lie together on a sofa. She, trembling with relief and uneasy triumph, believes she has won him back. Plath wants him to leave his new lover, Assia Wevill; he informs her, the mother of his two children, that he can't leave his girlfriend, because she's pregnant. Yet earlier, when he leaves Plath in Devon, he ignores their toddler in the yard and drives away.

Life and hard facts overwhelm the film. Everyone who is interested already knows the story. Still ambivalent about all the biography and remaining more drawn to the finest of Hughes's instinctive nature poetry than to the more cerebral Plath, who even at her most emotionally intense remains an intellectual poet, I was astonished and convinced by Paltrow's mood shifts.

Her Plath is neither a saint nor a victim but very much the clever, headstrong gambler in search of love and intent on fame that Sylvia Plath appears to have been.

It sounds simplistic, but a girl with as developed a sense of self-drama as Plath was never going to settle for a suburban Mr Nice. She didn't. Her dangerous impulses, combined with choosing a dangerous mate, compounded her fate and her poetic legacy and conferred immortality.

Sylvia opens on Friday