Giselle, Royal Opera House, London

When I missed Alina Cojocaru's first Giselle, in 2001, I missed an event. The ballet, choreographed by Petipa after Coralli and Perrot, is one of the great ballerina roles. A peasant girl is betrayed by her aristocratic lover, goes mad and dies. Returning as a ghost, she protects him from the wilis - the vengeful spirits of jilted girls who catch men and dance with them until they die. Giselle obviously suits Cojocaru's waif-like physique, dramatic focus and light jump, and she was promoted to principal at the end of that first performance.

All those qualities were there in the first night of this revival, but it didn't take off until the mad scene. Cojocaru and Johan Kobborg, dancing her lover Albrecht, were on uneven form. Clean dancing, plenty of sharp dramatic detail, but at first rough pacing took the edge off the performance.

She's careful, for instance, to give repeated steps a different inflection. Giselle's dances with Albrecht are on a larger scale, dwindling to an embarrassed shuffle as she explains to her disapproving mother. With Cojocaru you couldn't miss the contrast, or its dramatic point. Still, her first dances could be brighter and bolder, with more freedom through the upper body. She breaks her solos into individual steps, rather than letting a dance impulse carry her on. Kobborg showed a similar loss of momentum. There were lots of intelligent details - you can always see him thinking out his next move, without considering long-term consequences. In the solos, jumps and beaten steps shone out as if spotlit but these effects were weakened by lack of pace.

Sandra Conley, as Giselle's mother, showed more sense of dramatic shape than anyone around her: her mime scene is difficult and complicated, but her conviction carries the audience through it.

Peter Wright's production doesn't encourage romantic intensity. Between the messily encroaching forest and Giselle's mother's logpile, John F Macfarlane's sets only just leave room to dance. The peasants go dutifully through the celebration of the new vintage, with no verve or buoyancy to the corps dances. (The peasant pas de six, led by Laura Morera, was a crisp and welcome exception.) The orchestra had a bad night under Boris Gruzin, with hoarse brass and melodramatic percussion. Does the heroine's death really need a cymbal crash?

Cojocaru's mad scene broke through the general stodginess. When she pulls her hair down, looking with clouded gaze through wisps of hair, she carries her small head more loosely. Her broken gestures are clearer than the small, neat acting of the first scenes, projected more strongly.

The wili dances of the second act, the ballet's great corps scenes, aren't well served by Wright's naturalistic production. Individual steps are well danced, but the Royal Ballet corps is encouraged to tell the story through the mime scenes, not through the formal sweep of the choreography. They're careful about gestures of rejection and threat, but don't put that cold strength into grouping and phrasing. These wilis could be more powerfully dramatic if their dancing were more powerfully classical.

Cojocaru improved throughout the second act. Her line becomes more fluid, weightlessly smooth, with more texture to the footwork. Kobborg matches her for lightness and speed. As before, they need more continuity, breaking the act into different dramatic sections rather than building from one dance to the next. Even so, I started to see why Cojocaru is a natural Giselle.

The whole ballet should tighten up later in the run. This first night was uneven all round. As Myrtha, the queen of the wilis, Mara Galeazzi was fine in the fast allegro dances, but weakened whenever she slowed down. Her balances were steady, but her line isn't grand enough for those held poses. As Hilarion - the peasant who loves Giselle unrequitedly - Martin Harvey jumped and acted strongly, but his mime was unnuanced. The corps danced well enough to make me wish they had a stronger production.

To 7 February (020-7304 4000)