The Kirov Ballet, Royal Opera House, London

Dated, vulgar, gawdy, implausible... in a word, delectable

The times they are a-changing, and nowhere more than at the Maryinsky Ballet of St Petersburg, better known to British audiences as The Kirov. It's significant that Russia's premier ballet company, with its unbroken line of descent from the heyday of the court of the Tsar, should have reverted to its pre-Soviet name - even if the rest of the world seems peculiarly resistant to it.

For the past 10 years have seen The Kirov steadily revamping its repertory, purging its 19th-century classics of the ideological and aesthetic dictates of the Soviet era and adding "modern" ballets from the 20th century, though as yet 1950s Balanchine is about as modern as it gets.

But this rejuvenating mission works in reverse, too. And some of the most remarkable products of the new regime are painstaking reconstructions of how the old ballets would once have looked. The current three-week London season promises a newly restored Bayadère, reversing a century of random edits and alterations. New too, or rather newly old, are restorations of Nijinska's Les Noces (1923) and The Rite of Spring (1913).

But lest anyone think ballet's most celebrated style supremos are turning into museum curators, the company launched its London season with a party, and a wild party at that. Le Corsaire is the craziest of 19th-century relics, a product of a time when ballet was conceived as much as exotic circus entertainment as a vehicle for art.

Pirates, slave girls, pashas with ridiculous false noses, and a souk's-worth of bra jewellery conspire to turn the bones of Byron's verse-story into a Vegas floorshow. Yet Petipa's choreography - a veritable lexicon of possibility in classical style - grounds the whole affair in the most satisfying artistry.

With its shipwrecks and kidnaps and dastardly disguises the plot doesn't bear too much analysis. But the glory of the ensuing mayhem is that it affords such exuberant excuses for dancing. From the first gazelle-bounding entry of Medora's women friends, to the belly-dancing slave auction, to the pirates' machismo stomp, within the bounds of classical style it can seem as if every variant on human motion is there.

And yet Corsaire also manages to operate as a technical showcase, not just from one principal couple, but from a whole squad of virtuosi, who between them give rein to some of the most awesome stunts in ballet. Rare as it is for a male soloist to win more cheers than the ballerina, in Corsaire's first-night cast it was young Leonid Sarafanov - a sprig of a boy fresh from the Vaganova School - who brought the house down with his twizzles and stratospheric leaps.

The efforts of Ilya Kuznetsov as Conrad, the noble shipwreckee, were almost as rapturously received. Romantically enhanced by a Björn Borg headband, his floppy hair flying, he presented the most lovable of heroes, the exertion of his beautifully padded jump never once clouding his frank and sunny smile.

Eavesdrop on any conversation about Russian dancers, and the words "thoroughbred racehorse" sooner or later pop up. But I've yet to see any animal as exquisitely put together as Svetlana Zakharova, whose limbs have the length and elegance of a wading bird's, yet who moves with the speed and elevation of a skylark.

Zakharova also hits all the right notes dramatically - fiery in her defiance as she's auctioned as a concubine, lusciously sensual in her love-ins with Conrad, full of girlish delight as she discovers that the devout monk begging alms at the harem door is her hero in disguise come to free her.

I haven't enjoyed myself so much in years. But do the Russians see how OTT this all is? I'm not sure they do. Russia seems to have bypassed the fashion for irony in the past 20 years (you will recall they had more pressing issues to tackle), and The Kirov dancers' enthusiasm for Corsaire's absurder twists is refreshing and endearing.

This is one eyeful of a production: an explosion of iridescent peacock feathers in the harem, a storm at sea so real you think it must be film (yet the waves, you later realise, are only a slightly more sophisticated version of rippling bed sheets). The famous jardin animé scene, with its surprise water fountains, was state-of-the-art in the 1850s. It's to the credit of this fabulous production that it makes our hearts skip a beat still.

The Kirov season continues at ROH, London WC2 (020 7304 4000), to 9 Aug, closing with two further performances of 'Le Corsaire'