Apollo/ A Midsummer Night's Dream, Mariinsky Ballet, Royal Opera House

The ballerina claque wars that generally accompany visits here by the Mariinsky Ballet are raging particularly feverishly this year, but it all falls silent when Uliana Lopatkina makes one of her increasingly rare appearances. So much noise is focused on legginess or hip flexibility of these size-zero ballerinas, and yet the Mariinsky knows more than any other company in history that it is not body but mind that matters in the final analysis.

Lopatkina once set the new bar for physicality in St Petersburg 20 years ago, being so very tall, so very slender, though size 41 feet and a strong chin had to be dealt with in terms of line. But there is nothing like a problem to bring out the best in you. Her former partner Igor Zelensky also had a big chin - he once told me that he worried constantly about it, that making his head graceful was a preoccupation. And of course, that chin preoccupation helped Zelensky become the noblest of them all.

So too with Lopatkina. The exquisite flow of her dancing has been produced by the physical intelligence of a girl built on grandly architectural lines, watered by her theatrical sense of musicality and awareness of the poetic space of ballet. Her Swan Lake iconography is so extraordinarily potent that she has become embalmed in popular imagination in these classical otherworldly tutu roles. But oh boy, can Lopatkina tickle and entertain too, and her Titania gave Balanchine’s A Midsummer Night’s Dream a laughing wit that - I don my tin hat here - is sorely needed in this ballet.

Ballerina wars come no fiercer than the argument over which is the finer Dream ballet, Balanchine's or Ashton's

Even ballerina wars don't come fiercer than the argument over which is the finer Shakespeare Dream ballet, Balanchine’s 1962 version for New York City Ballet or Frederick Ashton’s 1964 one for the Royal Ballet. You’re comparing two geniuses, two quite different treatments, so it is down to taste. Where Ashton confidently chopped the Shakespeare play down to a 50-minute ballet of distilled wit and amorous crispness, his Russian-American contemporary doubled the length to 100 minutes and kept all the characters. To me the result lacks Balanchine's usual musical eloquence, as well as being dramatically awkward. The extra helpings of Mendelssohn inside his well-known incidental music lead to longueurs and oddly staid set-pieces looking back to a leisurely 19th-century imperial ballet genre where characters have names but no actual character.

There are couples everywhere, Titania and Oberon, Hermia and Lysander, Helena and Demetrius, Theseus and Hippolyta, but the fairy and real worlds are not strongly differentiated in choreographic accent (and the Mariinsky's lighting and costume designs - originally for La Scala by the impolitely misspelt Luisa Spinatelli - don't help). The lovers’ comedy squabbles are given unwarranted solemnity by being set to the long Fair Melusine overture, and saddled with more head-clutching than is strictly amusing. I question whether it was Balanchine’s fault or the Mariinsky’s that Puck gave a cheesy little wave to the audience as he leapt on stage - “Look at me, folks!” Vladislav Shumakov signalled, with an exclamation mark in every gesture - but Balanchine’s choice of children to play the fairies also prioritises cutesiness over fairy sophistication.

What is arresting, though, is that where Ashton’s culminates in a lovemaking pas de deux for Titania and Oberon that is the highest, most sumptuous hippy-era sensuality, Balanchine gives none of the named couples the major pas de deux. The glowingly serene duet at the mass wedding is for a separate “divertissement” pair, standing for all the lovers. The other two duets are for Titania in her boudoir with men other than her husband - or with creatures, for one ridiculously sweet duo is of course with Bottom. First, though, is her stately duet with an anonymous Cavalier. When performed, as many Titanias do, with queenly hauteur, ignoring their servile porteur, it can be a starchy affair. Lopatkina, though, made it a deliciously warm conversation with a dinner guest, here Andrei Yermakov - not flirtatious exactly, but a reminder that these are adults, that this parade of arabesques and promenades is the equivalent of a formal discourse within which smiling glances may show pleasure in the other person's company. To see such a sophisticated, glorious creature utterly infatuated with a donkey minutes later was all the more painfully funny.

Now 40, she dances, how can one say - bonelessly? She seemed to tread without weight, as if stepping on leaves on trees, or perhaps on the air. I suspect it is that Lopatkina simply decided to be a fairy in a parallel world, and so she did the hard technical work to become this fantasy creature who cheats gravity.

Oxana Skorik, who danced the divertissement pas de deux, is one of the hapless artists subjected to the aforementioned claque wars. She has the standard willowiness of today, the graceful finesse and nobly presented beauty of a young classical Mariinsky ballerina, but physicality alone is not quite enough to be interesting when next to you Lopatkina is giving a master-class in why it all matters.

Another much-debated new Mariinsky hire is Kristina Shapran, seen in London a year ago in the Stanislavsky Ballet’s Roland Petit Coppélia with Sergei Polunin, and I felt once again watching her Terpsichore in Apollo, paired on this Balanchine programme, that she needs to grow into her pretty legs and communicative face. Let Terp be her guide - both she and Skorik need to deepen their technical intelligence if they are to unify their motion into imaginative dancing. It’s all in the mind now.

In just 30 minutes the god of sun and art is born, is unswaddled, and then ushered into the great questions of creativity

Still, Apollo was performed with pleasing care - to fine playing from the Mariinsky Orchestra under Gavriel Heine - and had a compelling central interpreter, the alert, nobly expressive Alexander Sergeyev (pictured above with Shapran, © Valentin Baranovsky/ Mariinsky). True, solar flares did not quite shoot out of his heels (those sudden foot twiddles should be like a match striking fire). But Sergeyev’s responsiveness and instinctive grandeur, belying his young appearance, brought alive this endlessly enriching exchange between Stravinsky’s music and Balanchine’s choreography.

If Midsummer Night’s Dream meanders, Apollo, the masterpiece of Balanchine’s Ballets Russes youth in 1928, is the tautest possible examination of being alive. In just 30 minutes the god of sun and art is born, cries, is unswaddled, and then ushered into the great questions of creativity: of music, literature, mime. As the metaphor proceeds for the birth of dance, the birth of thought itself, the god and his three muses strike a sunburst and the dawn breaks. There is a special poignancy in seeing this astounding work being performed by new acolytes of Balanchine's alma mater, warmed by its bright power and amazing beauty almost 90 years later.

• The Mariinsky Ballet perform three more programmes at the Royal Opera House, till 16 August

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Overleaf: watch the La Scala 2007 recording of Midsummer Night's Dream in the same Spinatelli designs, starring Alessandra Ferri and Roberto Bolle