Dance Giselle Royal Ballet, Covent Garden English National Ballet, Coliseum

Imagine an actress who only gets to act Lady Macbeth twice a year. You wouldn't expect much of a performance, would you? Yet crowded company schedules can mean that ballerinas often get only a couple of cracks at some of the most taxing roles in the repertoire. Two versions of Giselle - one new and one traditional - have been showing in London, but both led by ballerinas who manage to craft thoughtful interpretations without the luxury of frequent repetition.

English National Ballet's 1994 production of Giselle updates the action from medieval Ruritania to a luxury hotel in the Tyrol of the Twenties, a development that doesn't have nearly as much impact as you might expect. Apart from the maids' and bellboys' uniforms and Albrecht's arrival in a Silver Ghost Rolls-Royce (which gets a big and very incongruous laugh), the scenario differs little from Mary Skeaping's much-loved earlier version. Friday's Giselle was Josephine Jewkes, the company's only English principal, who danced the first act with an air of anxious foreboding. Some dancers allow their Giselle a little maidenly glee in the pastoral sequences, but Jewkes will have none of it and her unease builds steadily and inexorably to a fine mad scene. Act 2 begins severely overcast by industrial quantities of dry ice. This clears to reveal the avenging tribe of ghostly maidens. The Twenties influence is glimpsed in the wilis' costumes and the traditional colour scheme is ditched in favour of a dingier hue - not so much Brilliant White as Old Bra. The neophyte Giselle comes among them and Jewkes excels here in the adagio passages, which she inhabits with a somnambulistic languor until her body finally dips and folds back down into her early grave.

The Royal Ballet's Sarah Wildor danced Giselle twice at Covent Garden last year. She is dancing it twice this year. If she plays her cards right, she might get a couple of goes in 1997. Despite this, she can give a performance of astonishing power and sensitivity. One shudders to think what she could do with the role if she had more time to work on it. Last year's partner was the posturing and unresponsive Zoltan Solymosi, who has since left the company. His place has been taken by the handsome home-grown Stuart Cassidy, who suited her far better.

Endearing as a kitten, Wildor's Giselle is a child-like creature only truly happy when dancing solo. Her obvious terror of physical contact carries echoes of her fine interpretation of MacMillan's violated virgin in The Invitation. The cloud of corn-silk blonde hair, the bee-stung mouth and trembling lower lip make her appear on the verge of tears at the best of times; when driven mad by the thoughtless betrayal of her aristocratic lover, her misery is shared at the back of the stalls. Her performance in Act 2 was equally successful. Wildor, like Jewkes, manages to combine the stiff technical demands of Giselle's ghostly persona with the ethereally droopy wrists and submissive head so necessary for the successful evocation of the afterlife.

If there is a flaw in her performance, it is in the absence of unalloyed girlish joy in her first act to contrast with the woe of the second. But the decision to present Giselle as a morbidly sensitive and acutely vulnerable individual is sustained with such thoroughness and conviction that one is forced to view the lack of gaiety in the role not as a failing, but as a new and terrible strength.