Todd Haynes’s film about Bob Dylan is one of the greatest rock’n’roll swindles of all time. The hero is “not there”. He’s officially a ghost. Yet this mythic account of his life is one of the sexiest pieces of cinema I’ve ever seen at a festival. Six brilliant actors play Dylan and they are as madly various as the artist’s album covers. For the record, Dylan himself was so bewitched by the project that, for the first time, he yielded up his precious song rights.

The sprawling anthems provide a spine to Haynes’s fabulous mulch of newsreel and concert footage. He’s perfectly aware that the history of indie cinema chimes wonderfully with Dylan’s growing power.

The crazy gamble – casting different actors to express different parts of Dylan’s elusive career – is repaid by magic. Everyone takes on a name, job and demeanour that is only inches away from the musician’s public life.

Christian Bale, Ben Wishaw and Heath Ledger are unspeakably brilliant as various shades of Dylan. They wrestle with Nixon, fame, drugs, Christianity and celebrity, more often than not in ravishing black and white. They are mostly trapped in ghastly interviews. The television footage is extraordinary. You can see how the politics of celebrity are wired into Dylan. His curmudgeonly attitude to fame speaks volumes.

This is an admission that film has a grip beyond words. The chemistry is chaotic. Some Bobs have more attractive jobs than others. Heath Ledger is butch Bob. He has a fabulously attractive wife (Charlotte Gainsbourg). The big mistake is cowboy Bob. Richard Gere is totally weird as a backwoods actor in McCabe & Mrs Miller – one of Dylan’s doomed Hollywood outings with Sam Peckinpah.

The real star is Cate Blanchett.

She is the most unlikely Bob Dylan in the world. Yet she is simply fabulous as the frizzy-haired 1960s troubadour who is staked out by the BBC’s media inquisitor, Mr Jones (Bruce Greenwood), to test if Dylan is a fraud. Their documentary debates in a limousine riding through London are mint perfect. Yes, it’s an insane piece of casting. But Blanchett is superb. She drops a vocal octave, writhes around on Andy Warhol’s sofa without missing a beat, and, crucially, never gives you much room to think about her breasts, even when she is scolding her lover, Coco Rivington (Michelle Williams).

Blanchett straddles the most interesting stretches of the film like the scrawny bard in his pomp. She inhabits Dylan at his most political, stoned and vulnerable. The medley of battles with the Establishment, particularly a media hell-bent on crippling Dylan, is marvellous. My only reservation is that half the other Dylans can’t hold a lighted candle next to her.

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