Julian Schnabel's film, for which he won the Best Director prize at Cannes, is substantially a true story, and an extraordinary one. Jean-Dominique Bauby (Mathieu Amalric) was the multi-talented, womanising editor of Elle, the French fashion magazine, when he had a massive and paralysing stroke.

Though he could still see and hear, he could only move his eyes. For a youngish man so full of the life force, it looked a hopeless case.

But a speech therapist (Marie-Josée Croze) suggested a means of communication by which she arranged the alphabet in order of the most frequently used letters and he chose a letter by blinking. This was the way he spoke and dictated his memoirs, published in 1997, shortly before he finally died.

Schnabel is the New York painter turned film-maker who made Basquiat, about a well-known graffiti artist, and Before Night Falls, about the prosecuted Cuban poet Reynaldo Arenas. This time, however, he has no delusions about his subject. He knows the man was far from an angel but somehow achieved in his paralysed state more than when he was well.

The film, in French, with a screenplay by Oscar-nominated Ronald Harwood, uses flashbacks to tell us about him, his mistresses, the faithful mother of his children and his work.

He adds the locked-in man's fantasies about sex, food and the movement we all take for granted. Above all, he shows Bauby lashing out against his fate in the only way he now can.

At one point, Max von Sydow, as his veteran father, tells him that having a mistress is no excuse whatsoever for leaving his children. He is clearly no paragon. But he becomes a kind of hero and we admire him for it, wondering what we might do in the same circumstances.

Though Amalric is excellent, making Bauby full of self-pity but consistently refusing to engender anything as obvious as pity from us, Emmanuelle Seigner as the mother of his children and Croze as his nurse, and a sort of fantasy sexual partner, are equally notable.

Janusz Kaminski, the cinematographer, using cloudy hand-held shots as Bauby regains consciousness and otherwise filling the screen with an elegant lightness, adds a great deal to the proceedings.

The film is not above a little cheating for the sake of its audience's susceptibilities, but at the end, what we get from it is the indomitability of the man and the patience and care of those around him.

In this way, The Diving Bell and The Butterfly is the reverse of depressing - even if it's not quite as moving as it would have been had sentiment been excluded.