DANCE / Messenger from the gods: Judith Mackrell is spellbound by Michael Clark's O at the Brixton Academy

Brixton Academy is the place to watch Part 1 of Michael Clark's O, at least if you're sitting in the circle and aren't being crushed by the standing crowd below. The camp folly of its interior (all fake Italianate facades), the cigarette smoke, the cavernous space in which Clark's preferred high-volume music can racket - all provide the slightly illegal, clubby atmosphere he courts in his work.

The dance's first section also uses this clamorous background to point up its own extraordinary lucidity. While something of the old anarchist Clark remains on stage (in one corner his Mother, Bessie, is lounging on a sofa, watching TV as neo-punk rock belts round her ears), the dancers themselves are stretching through movement that is hypnotic in its clarity, its exquisitely skewed shapes and its taut rhythms. Clark has rarely made choreography so uncluttered, and has rarely allowed us to luxuriate so long in the uncanny beauty of his own dancing, with its alert animal tension and voluptuous relaxation.

Watching this section, it seems that Clark has reached a welcome truce between the washy and the sublime in his art. But it doesn't prepare us for what happens in the second part, which is danced to Stravinsky's Apollo and shows Clark, for the first time, letting his classical instincts fly free. Suddenly Brixton Academy is an absurd place to be. Restive fidgeting and clanking glass distract from choreography that holds some of the most purely and limpidly beautiful dance I've ever seen.

Given the near perfection of Balanchine's original Apollo, Clark is taking a serious risk with this piece. But he makes both the music and the subject his own. There are, for instance, two Apollos and two births. The first is a sly joke as Daniel Squire wriggles from under a duvet covering Bessie Clark's legs. The second is a breathtaking theatrical coup. As lights brighten over a cube of mirrored glass, you see a foetally crouched Clark gently stretching his body to the accompaniment of four reflections of himself. The slow discovering grace of his movement is like the beginning of Dance.

For minutes you watch him testing his limbs, until he pushes through his glass womb on to a stage that is all white light and space. The dancing that follows is almost hallucinatory. Clark himself seems a definitive Apollo, not simply because of his God- given beauty (the poise of his long neck and limbs, the instinct for line that makes him incapable of a false move), but also because his current style mixes a pitch of classical sophistication with a peculiarly touching primitivism.

The latter is partly defined by references to Nijinsky's early ballets - an archaic flattened profile, a springing, startled leap - but also from the way Clark twists familiar steps into movement that seems to be finding itself for the first time.

But O isn't just a vehicle for Clark's divine dancing. Some of its most perfect steps are made for his three (excellent) women. Clark gives them slow classical adages that are cantilevered perilously off centre, their lines made both lavish and strange by proud circles of the head, sensuous curves of the hips and hieratic commands of the arms.

My first thought on watching O was that I had to see it again. My second was that it should be staged with Balanchine's Apollo to to make a night in ballet heaven. Sponsors, a life support for dance, don't always get sufficient credit, but O was funded by Prudential and Becks Beer who should both feel proud.

'O' continues at the Brixton Academy until 25 June. Booking: 071-924 9999