Ondine, Royal Opera House, London

An 'Ondine' that's to die for

Frederick Ashton's Ondine is a curious, troublesome ballet. This 1958 tale of a water-nymph and her mortal lover was Ashton's last three-act ballet, his only full-length work to a modern commissioned score. It has ravishing images of water, bodies ebbing and flowing. Yet Ashton didn't take naturally to Hans Werner Henze's music, and the dramatic structure is uncertain. The ballet has thin patches, quaint hermits and dutiful divertissements.

Frederick Ashton's Ondine is a curious, troublesome ballet. This 1958 tale of a water-nymph and her mortal lover was Ashton's last three-act ballet, his only full-length work to a modern commissioned score. It has ravishing images of water, bodies ebbing and flowing. Yet Ashton didn't take naturally to Hans Werner Henze's music, and the dramatic structure is uncertain. The ballet has thin patches, quaint hermits and dutiful divertissements.

In the Royal Ballet's superb revival, however, you hardly notice the creaks. The company has celebrated Ashton's centenary this season, and his ballets have dominated the repertoire. These dancers now look at home in his style, flowing easily into lyrical lines and brilliant, burnished footwork. They move with a confidence and sweep that draws the ballet together.

Henze's music isn't always danceable. Washes of sound ripple on inconclusively, broken by spiky textures, but Richard Bernas conducts a dynamic account of the score. The orchestral playing is warm and detailed, but it is always going somewhere.

In spite of Henze's score, Ashton's theme was thoroughly old-fashioned. As in La Sylphide, as in so many 19th-century ballets, the hero is torn between two women, between the domestic world and an enticing vision. Ashton's ballet shifts, not always easily, between modernity and the wonders of 19th-century stagecraft. It is built firmly around the ballerina: Ondine was Ashton's last major work for Margot Fonteyn. It fell out of repertoire once she stopped dancing it. The ballet is built around its heroine, and mortal roles are weakly characterised.

Alina Cojocaru is a quick, delicate Ondine. Her look of youth and vulnerability underlines the character's innocence. Ondine causes havoc without noticing it. Travelling by ship with her lover Palemon, she sets the waves heaving and dancing, but is shocked by the effect of the storm on her human companions. Cojocaru's dancing is full of darting, silvery detail, with clear musical flow. This was her debut, and her Ondine needs more authority - she doesn't yet use her full stage presence. She's best in the last duet, when Ondine returns to the faithless Palemon (Federico Bonelli) and kills him with a kiss.

Palemon is a blank, spare role. Ashton didn't give him much dancing, and Bonelli has to do a lot of standing about. But how he stands! His Palemon is another innocent, caught up in the world around him. Staying still, he seems fully involved in the ballet's world, and in its music. At the start, we see him courting Genesia Rosato's wilful Berta. When he offers her an amulet, the gesture is both tender and tentative. Entranced by Ondine, he's suddenly confident: a man enchanted. His one solo is danced with rich texture.

Rosato makes the spiteful Berta beautifully feminine, enticing Palemon as much as she quarrels with him. As Tirrenio, Lord of the Mediterranean Sea, Martin Harvey dances with bold, muscular detail.

The last-act divertissement is the weakest thing in Ondine. Confronted by Henze's flashing piano solos, Ashton seems to have poured in everything except inspiration. At this performance, those dances were polished to brightness. Laura Morera is wonderfully witty, swinging her hips and fluttering her fingers. Ricardo Cervera is dazzlingly quick and bold.

Lila de Nobili's designs put the ballet into a Regency Gothic world. Her sets are full of subtle perspectives and shimmering brushwork. Sadly, John B Read's lighting doesn't really do De Nobili full justice. Her landscapes are mysterious enough without his navy-blue lighting.

Frederick Ashton drew his water-nymphs into rivulets, waterfalls, tides, their arms drifting and curling like delicate fronds of water weed, their groupings floating adorably between Busby Berkeley and classicism. The Royal Ballet corps flow and sparkle like the sea in sunshine.

To 24 May (020-7304 4000)