Cannes 2007 has come up with an amazing scientific breakthrough. The solution to climate crisis, we are learning, may be stellar power, not solar power. By sheer force of glitter and glamour, an army of stars is now powering an entire French town. Night has become day. Music issues from unseen sources, all along the palm-lined Croisette. Firework displays erupt spontaneously at midnight. The hungry are fed by lunches, dinners and parties, which seem to appear from absolutely nowhere. (Forget loaves and fishes. Today’s miracle is champagne and foie gras.) All this is due to the power- generating ability of celebrity.

As if the array of top directors were not enough – a dozen or more living legends trucked in to be 60th festival guests – we have just had the ultimate visitation: Brad and Ange. Pitt and Jolie stepped off a cloud after their non-stop flight from New Orleans or Namibia or Neverland and increased the Côte d’Azur voltage to overload. (Nearby Monte Carlo was reported to have had a blackout.) Pitt came as the star of Ocean’s 13, a treat awaiting us in the final days, and also as co- producer of the keenly anticipated A Mighty Heart, starring his wife.

A gasp of horror had gone out from everyone but me – my response was a scream – at news that the lead female role in Michael Winterbottom’s reality-based terrorism tale would be played by the overpublicised diva with the hornet-stung lips. Lara Croft as Mrs Daniel Pearl? Hollywood’s top-dollar sexpot as the tragic widow of a beheading that set the benchmark for cruelty in this long, latest chapter of world jihad?

We reckoned without – yes, again – stellar power. This not only energises Mediterranean fishing towns, it turns bimbos into Bernhardts. That Jolie can act as well as pout is finally proved by this French-accented turn, moving and modulated, as the woman whose husband became roadkill on the roadmap to a never-never Middle East peace process.

Winterbottom, who made In This World and The Road to Guantánamo, can do political cinema in his sleep but doesn’t allow himself to nod off here. The pace is tingling, the sense of authenticity thrilling. He and writer John Orloff resist an imaginary enactment of Pearl’s own ordeal. The Wall Street Journal reporter (Dan Futterman) is seen mostly in flashbacks, which function as agonised memory-prompts while his wife Mariane learns to convert hope to hopelessness. The Pakistani police bustle; the Anglo-American diplomats search every avenue, only to find cul-de-sacs; the ghastly videotape finally comes to light.

Could Winterbottom and Orloff have given the tale a bigger acoustic? Could they – should they – have dared to give offence by letting the terrorists articulate their cause? (The Road to Guantánamo allowed Islam its say.) Probably not. The world is still too young to treat Pearl’s death as anything but the inhuman act that to feeling human beings it was. The film opts to depict a single, simple, shocking tragedy. It does so with force and skill, helped by Jolie’s impassioned heroine.

A Mighty Heart was shown outside the competition. In the Palme d’Or race, the pacesetters are still those announced in my last dispatch – Romania’s Four Months, Three Weeks, Two Days and the Coen brothers’ No Country for Old Men – though a third contender is moving up fast in the betting. Marjane Satrapi’s Persepolis (see interview below), a French-Iranian animated feature based on author-cartoonist Satrapi’s autobiographical graphic novel, got a standing ovation at the Palais. The black-and-white drawings seem plain at first but the script and characters blossom into life in a tale of three cultures – Iran, Austria and France – full of wit, compassion and, where appropriate, crusading indignation. Satrapi’s savage attack on life in her native country after the Islamic Revolution has brought an official protest from Iran, claiming that the film’s picture of repression and persecution is biased and exaggerated. Is it? Not by the facts at most westerners’ disposal.

Not all has been glitter and glory in the Golden Palm programme. Starriness stood in for substance with two flashy vacuities from Cannes veterans Gus Van Sant and Quentin Tarantino.

Van Sant’s Paranoid Park is a rare dud: 85 minutes inside the vacant mind of a Portland, Oregon, skateboarder involved in an accidental murder. Transposed from a novel by Blake Nelson, Van Sant’s hero is played by Adonis newcomer Gabe Nevins with all the vitality and complexity of a gay teen centrefold. There is something sickly about the film’s posing of him in endless tableaux of synthetic Passion – a Saint Sebastian in the shower, a Jesus in the nocturnal Gethsemane of the skateboarding park – while the soundtrack woos us with selections of everything from heavy rock to J.S. Bach.

Tarantino’s Death Proof at least has energy. Prised from the commercial disaster that was (in the US) Grindhouse, a pastiche of a cheapie double-bill with one mini-feature from the Pulp Fiction master and one from Robert Rodriguez, this blend of girlie action flick with retro car-chase movie scores nil for artistic expression but six for amiable delinquency. A carful of Amazonian nymphets is chased and terrorised by Kurt Russell as a tyre-scorching psycho. Who will kill whom? We hardly care. But at least some of the stunt action keeps us alert.

The American director with the best hope of a prize, Coens apart, is Julian Schnabel. The painter-filmmaker lavishes visual skill on The Diving Bell and the Butterfly, a French-language adaptation of the unique memoir “written” by Jean-Dominique Bauby, a paralysed stroke victim who could only blink his prose, letter by arduous letter, to a dictation-taker. Early scenes are done literally point-of-view-style, the images blurry, swirly, near-psychedelic and shot by Schindler’s List cameraman Janusz Kaminski.

Ronald Harwood’s script wisely declines to make a fable of ambition’s fall – Bauby had been the editor-in-chief of Elle magazine – and takes the more grounded, poignant route of narrating an Everyman’s victory of determination over disability. Actor Mathieu Amalric is reduced to one staring eye (the other, failing to irrigate, had to be sewn shut) and a lopsided mouth. But the surrounding cast has compensating animation, even if there is an odd preponderance of supermodel-pretty women among them, as if Elle magazine had come to life at Bauby’s bedside.

Prettiness is seldom in sight in Béla Tarr’s The Man from London or Ulrich Seidl’s Import/Export. Middle-European miserablism gets its time on the Med. Cannes viewers, flushed from their latest lunch on the littoral, sat with jaws agape, or in slumbrous cases eyes sealed, as the pile-driving pessimism of Tarr’s Hungarian film noir and Seidl’s Austrian film pâle went on and on.

In Tarr’s Magyar makeover of a Simenon tale, the screen is steeped in Piranesi tangles of black and white – often beautiful – while the even more tangled story gives us murder and robbery. Midway, there is the surreal appearance of a Hungarian-speaking Tilda Swinton. Seidl (Dog Days) makes Mike Leigh seem a merrymaker with his latest slab of working-class realism. The criss-cross stories of a Ukrainian cleaner in a Viennese geriatric home and an Austrian wide-boy selling gumball machines in Ukraine, helped and hindered by his stepdad’s drunken womanising, have a bracing realism, if a somewhat remorseless nihilism.

And so the days go on, yo-yoing between the real and the surreal, the good and the bad, the sublime and the not-so-sublime. It is all huge fun, of course. You never believe you are on Planet Earth when in Cannes. How could you, living in so many parallel universes and emerging from cinemas each midnight into the unlikeliest universe of all.

What is this place where everything sparkles, where a velvet sea laps a palm-adorned promenade and where every time you pass a certain set of red-carpeted steps, someone famous is climbing up or down them? These people are roared at by rubberneckers, their VIP images magnified by giant screens at either side of the ascent. You sometimes catch the stars looking at these screens as they exit the limelight, rather like batsmen appraising their dismissals at Lords or the Oval.

When you least expect it, you yourself – a critic, an innocent, a harmless drudge – may be kidnapped for apotheosis. This week, I had a medal pinned on me by the Cannes rulers for services to writing about films and festivals. I suspect it was for still being alive, after sitting through countless movies over countless years. (I have counted the Cannes attendances, actually: 34.) I wear the medal proudly. And I sleep with it, under my pillow, on the rare occasions I have time for any sleep at all.