National Ballet of Cuba, Sadler's Wells, London

Take also Alicia Alonso, director of the National Ballet of Cuba, here on its first visit to London since 1984. Although not quite as old as Giselle - she's a mere 84 - she remains very much in charge: a symbol of iron will. Aged 21, she began to lose her eyesight, but she still became a dance star in the USA, before founding, in 1959, a national company in her native Havana, with the support of Fidel Castro. Blindness has not stopped her from dancing into her sixties and beyond either: I remember her in London as Giselle, her fellow performers offering discreet hands to guide her on and off stage. Nor - bogglingly - has it prevented her from choreographing. The results are somewhat varying, but in this season's mixed programme, Magia de la Danza, her 1990 piece Gottschalk Symphony formed a rousing finale: classicism with a showbiz twist harking back to her Broadway days.

She fills the repertoire with her stagings of the classics, among them Giselle, the company's signature ballet. When the Cubans perform Giselle, you don't just witness the ballet speaking through the dust of centuries, but dancers blazing through the cardboard decor and school-play costuming. Finances may be tight, but the sincerity and self-belief of the dancers are boundless.

The ballerina Viengsay Valdés has a terrific jump and the control to modulate her phrasing, despite the jarring sounds coming from the Royal Ballet Sinfonia under Giovanni Duarte. She may not be one of the defining Giselles, the way Alonso was; but she never forgets that technique is a vehicle for expression, no matter how academic the steps. Her long first-act solo displayed not only lovely balances, but gentle charm, at one with a character that is both shy and playful. Giselle's love of dancing represents her love of life, a quality at odds with the death that is foreshadowed even as she performs her airy ballonné jumps. (It's her dicky heart that does her in, along with Albrecht's betrayal.)

Where some Albrechts are dastardly philanderers, Joel Carreño's anti-hero is particularly likeable, not so much two-timing as genuinely in love, so that his contrition is overwhelming when Giselle dies. The younger half-brother of American Ballet Theatre's Jose Manuel Carreño, he has the harmonious Carreño outlines, as well as outstanding stretch and precision, if not much elevation.

Victor Gili gave a vividly rounded portrayal of Hilarion, the lumpish rival for Giselle's affection. (Gili is rounded and lumpish in another way, suggesting a reckless off-stage love-affair with Cuban cuisine.) Another male principal, Rómel Frómeta, appeared in the minor role of Albrecht's equerry, but in the mixed programme his sensational tricks in the Don Quixote pas de deux had driven us wild, reminding us that this company has moulded the likes of Carlos Acosta. Frometa apart, though, evidence of male technical brilliance was apparent more among the corps de ballet than among the principals.

The Cubans have preserved the complete mime scenes, but also include material I've never seen. A return to historical sources? No, more like Alicia Alonso's second thoughts. Unlike the elaborations of other producers, though, Alonso's are never less than intelligently apt. I doubt Giselle's creators ever envisaged that their ghostly wilis would run on like automata, torsos bent with clockwork rigidity, feet moving as if they were ball bearings. But - wow! - how terrifying they are. They communicate perfectly the emptiness inside the graceful female shells, the machine drive to destroy. They trap their male victims inside circles as secure as barbed wire. When they form their famous diagonals, the inhuman unison is unforgettable, like a row of paper cut-outs.

Giselle is Alonso's triumph and when she arrived for the curtain call, in her scarlet dress, the ovation was rightly overwhelming. Her resilience has nothing in common with the ballet's fragile heroine. What happens after her is a whole other question.

Jenny Gilbert is away