La Bayadère, Mariinsky Ballet, Royal Opera House

The bayadere bears on her shoulder a vase of holy water, and the story of the ballet La bayadère is of her refusal to compromise. She could better her life in two political deals: become the high priest’s mistress, or later, when bitten by a poisonous snake, take the antidote and live on while watching her sworn lover marry the princess who he knows tried to murder her. She refuses both. She remains, morally, the vessel of a purity that it would kill her spirit to give up.

To stay so true to a principle isn’t only the stuff of fantastical ballet fairy tales. It has to be true of the interpreters in the theatre who bear other people’s work on their shoulders, often, in theatre, not very great work - yet in ballet these interpreters can turn even base stuff into something sublime. La bayadère is only a 19th-century exotic melodrama created in 1877 more with an eye to divert than to move, but it can become a masterpiece when it’s given a performance as dedicated to the holy well as it had last night, the final one of the Mariinsky Ballet’s 2011 tour to Covent Garden.

As my colleague Judith Flanders reports today, in the absence of a worthy Swan Lake production, it’s La bayadère that has to do the honours for showcasing the Mariinsky’s purest stylistic beauty, above all in its unspeakably haunting final act, as white-tutu’d angels pour out of the Himalayas, in the ultimate vision of all classical ballet.

And last night the corps de ballet lived up to the dream. A hypnotic file of ballerinas, in numbers that only the Mariinsky can field, emerged like glowing phantasms from the cavern, lilting forward and backwards in their arabesque parade, 32 identical shapes moving at all the same angles, hands and feet tapering in the same shining finish, the impression of multiple slivers of a new moon in remote, unattainable mountains.

Such simple, almost elementary steps these girls do, created by the miraculous choreographer Marius Petipa almost 150 years ago, but which the St Petersburgers have turned into their articles of faith. These are elementary ports de bras, elementary leg moves, letters of the ballet alphabet, the basis of the grand classical vocabulary, yet en masse, so deliberately, and so hallucinatorily produced, phrased with secret communal understanding, they become stanzas of poetry.

 And at the heart, as Nikiya, the story’s heroine, there was Uliana Lopatkina, who takes all this complex, dense, rich training and work, all the sweat and intention, and transfigures it so that there is no more work, there is no more training, there is no more effort - there is only the poetry (pictured below, Lopatkina with Ponomarev's High Brahmin).

Twenty years ago when she first featured as a teenage starlet on Kirov tours to the UK, because of her tall, serpentine body she was cast as a haughty sex slave in many a 19th-century ballet romp, mournfully dancing, irresistibly seductive, her eyes clouded, her mind on higher things. Capable of the most elastic contortions, she didn’t go the exhibitionist way of other Mariinsky ballerinas of similarly slender physique, she continued to deploy that fascinating bodily quality with a deeper and deeper inwardness and spirituality.

While it’s evident that the Mariinsky schooling could produce circus contortionists if it wanted to, what’s been evident, too, is that the great and pure artistry of Galina Ulanova, Altynai Asylmuratova and Lopatkina is a very live influence even in younger dancers taking the new liberal line. Anastasia Kolegova, the bad princess Gamzatti last night, epitomises the two polar impulses in conflict. She insists on slamming her leg vertically behind her at cost to grace and harmony, but her poised upper carriage and the inquiring bearing of her head implies that she may be asking questions about how to update her style without tainting it with vulgarity. I noticed that too in Alina Somova, the current princess of extreme physicality, who is by no means a lost cause to artistry and should be watched.

But La bayadère, which must originally have been fairly lighthearted with its slain tigers and processing elephants (Petipa's 1900 production pictured below), has also become a bit of a museum exhibit of what the Mariinsky elders have kind of decided is their style.

The music is forced into gluey tempi to obey certain movement rituals, at cost to dancing and theatrical momentum. Some of the mime passages for the High Brahmin, some of the featured dances of the Act III Shades scene, have become ossified audition pieces that blatantly spell out steps and hallowed gestures rather than delivering gorgeous dancing or expressive narrative. I wonder when I’ll ever see the Scarf dance in Act III given a natural musical tempo in Russian companies where those pirouettes can catch the wind and float on it, rather than being squeezed cruelly through the solo violinist's ego. Ditto two of the solos for subsidiary Shades, though Maria Shirinkina did a lovely job of the difficult second.

As long as the Mariinsky continues to deny the music’s natural impulses as much as Alexei Repnikov did last night with his charmless beating of loveable, waltzing Ludwig Minkus, so dancers will continue to come off stage at the end worried that they didn’t pull off the academic challenge, and audiences will keep saying to each other that it seemed far too slow in places. (The show ended at 10.45pm.)

One talks too much about the Mariinsky’s women but the men do not matter less. Daniil Korsuntsev, Lopatkina’s tall, discreet partner, is rarely given much attention - true, Igor Zelensky was her most thrilling partner in the past - and Korsuntsev isn’t a natural warrior-type, as Solor in La bayadère is supposed to be. Nor is he much able to play the two-timing bastard with the relish that others can provide. But he rose with dignified grace and accurate aim to his solos, and seems to know himself, he doesn’t force himself to be something else. That is a valuable quality, and it’s one that comes with experience and intelligence.

It’s the mark of someone who knows the purity of the water they’re bearing on their shoulder, and who will do their best to keep it clean and fresh. We need to see La bayadère occasionally in performances like last night’s, in Lopatkina’s above all, to remind us of our responsibilities.

• The Mariinsky Theatre Opera and Ballet 2011-12 season opens with Verdi's opera Aida on 26 September and Lavrovsky's ballet Romeo and Juliet on 29 September