He has made an indelible mark on British theatre. Yet it's the Russians who love Declan Donnellan the most, says Claire Wrathall. So much so, they've entrusted him with a 'Romeo and Juliet' for their beloved Bolshoi. There's one problem: he doesn't know the first thing about dance

Last autumn, in St Petersburg, I was chatting to a twentysomething member of the hotel staff about what to do the next evening. The Maryinsky? I wondered. The trouble with the ballet, Katya replied, is that the big names dance here so rarely because they're so often on tour. The opera, she reckoned, was a better bet, but its maestro, Gergiev, was away too. She hesitated a moment. "Really, what you should go to is The Winter's Tale at the Maly Theatre," she said. "I have seen it many times since they first performed it. Last month I took my 14-year-old brother. He thought it was fantastic, and now he is converted to theatre and Shakespeare."

Premiered in 1997, this Russian-language version was directed by Declan Donnellan. Highly regarded in Britain as co-founder and artistic director of Cheek by Jowl, as well as for his work at the National Theatre, where he is an associate director, in Russia he has the status of a master. So much so, that a month-long festival of his work has just finished in Moscow, the most talked-about production of which was a ballet he's created of Romeo and Juliet for Moscow's venerable and hitherto unadventurous Bolshoi.

Donnellan looks an unlikely choreographer. He has had no training in dance, nor experience of working with dancers. Though movement and music have been integral to many of his greatest productions - Fuente Ovejuna and Sweeney Todd, even Angels in America, all at the National Theatre - unlike most directors he doesn't "block" his actors. So his leads can be in entirely different places on the stage from one night to the next. His belief is that "changing from one shape to another keeps it fresh" and that "what we do has to be absolutely elastic". For the actors, says Mark Bazeley, who appeared in Cheek by Jowl's production of Tony Kushner's Homebody/Kabul in New York and London, it can be both "very liberating and also dangerous because when you go on, you don't know what's going to happen. It's very subversive and very challenging." And about as far removed as you can get from the rigid world of classical ballet, where every tiny gesture, the precise crook of each finger, is prescribed.

But Prokofiev's Romeo and Juliet, at least in Kenneth MacMillan's version for the Royal Ballet, is a work Donnellan has loved since 1969 when he was taken to see it at Covent Garden, aged 16 - one of what he calls "three epiphanic moments in the theatre". (The others were Peter Brook's trapeze-set A Midsummer Night's Dream and an RSC production of Dr Faustus.) "It made a burning impression on me, and I went back to see it again and again. It's impossible to say why, because dance is something I've never had explained to me. Yet the first time I saw it I felt I understood it. It's not an intellectual thing; I don't know anything about ballet. But when it's good, it's transcendent."

The genesis of the Bolshoi project dates back to last summer when the company's general director at the time, Anatoly Iksanov, having been impressed by the Falstaff Donnellan had directed at the Salzburg Festival, asked him to direct an opera. "Though I love doing opera, I said what I'd really like to do is a ballet of Romeo and Juliet. Only Russians would be mad enough to say: 'Yes, of course you can.'" With his partner, Cheek by Jowl's co-artistic director and the designer of all but one of its 25 productions, Nick Ormerod ("who does not like ballet at all"), he produced a scenario. This reduced Shakespeare's play, which Donnellan last directed nearly 20 years ago in Regent's Park (starring a fresh-out-of-Rada Ralph Fiennes), to a succession of scenes that could be communicated through movement.

It is, however, a play he's considered deeply over the years and written a book about, The Actor and the Target - published, incidentally, in Russian before it appeared in English. In some ways a variation on Stanislavsky's An Actor Prepares, it is a treatise for actors on overcoming blocks. It features an imaginary actress, Irina, as she prepares for the balcony scene, which Donnellan believes represents "our enduring image of romantic love, for there is no love without separation". In the play, he continues, "everything is pulling them apart - that seemed to be the choreographic essence of the thing." Though the book was written long before the idea of making a ballet became a reality, it is peppered with references to movement, to acting through one's body, to being "moulded by [one's] space".

But theorising is one thing, choreographing another. And in the rehearsal studio, things got trickier. For a start, though Donnellan has fluent French - still to some extent the language of ballet - he has only "terrible schoolboy Russian", so he and the company were communicating through interpreters. On day one in the studio with the two first-cast dancers, Denis Savin and Maria Aleksandrova, "I went to demonstrate a step which involved rolling on the floor and suddenly realised I couldn't stand up; they had to help me to my feet." He decided he needed help.

The choreographer he found was Radu Poklitaru, a young Minsk-based Moldovan whose chief influences, at least from the promo clips I've seen, would seem to be Mats Ek, at least in terms of its exaggerated, contorted, sometimes grotesque steps and lifts, not to mention the dancers' shrieks, screams and cackles. And perhaps inevitably there are echoes of Jerome Robbins in the crowd and combat scenes.

When the production opened in Moscow last December, it was, Donnellan says, "received incredibly well. Totally without controversy." Despite the Bolshoi's conservative ethos - "They're tarting the theatre up now to bring it into the 19th century, never mind the 21st" - no one cared that there were no pointe shoes; that it was in modern dress (modish jewel-coloured prom dresses); that Juliet marries in a trouser suit; and that Mercutio wears a frock. "There wasn't even a letter from 'Disgusted of Minsk'," he says. "I think maybe one person walked out, but for all I know they needed a pee. And the cast loved performing it." However, the British opera critic, Rupert Christiansen, who was at the first night, took a different view. Having dismissed the choreography as "inept", he wrote: "The first-night audience was plainly baffled." But he did concede that "the young might well adore it".

Since then it has played to packed houses, and after London the production is off to the USA and France. Donnellan is already getting offers from other dance companies to make more ballets. A new full-length narrative work for the Bolshoi has been mooted, as has one for the exacting Paris Opera Ballet who, says Donnellan, "have asked me to find some music that I'd like to make a story to".

His enthusiasm for the project is both infectious and rather sweet. "I'm not really a fan of the theatre," he says. "On the whole you tend to lose all your fan-ness when you work in something. But I haven't lost a scrap of it for the ballet. The dancers have so much talent, and I've never seen people work so hard. I think possibly the biggest thrill of my life was when some of those I was working with were in Spartacus. Nick [Ormerod] and I were in the director's box, which is about two feet from the stage, and two of them caught my eye and winked at us as they jumped. I thought I'd died and gone to heaven. I thought, I can't believe I know these people. I still can't really believe I've done it - with no previous experience. It's as if I've discovered a new career."

If so, it won't be the first time he's changed career. Having read English at Cambridge and "just acted for three years - very badly, but with great enthusiasm," he followed Ormerod, whom he met when he was 19, into law, and was called to the Bar in 1978. "I got my wig and gown and went into court." But his heart wasn't in it. Ormerod, also a barrister by then but a year ahead, quit to study stage design. Donnellan left too, hoping to pursue a career as a director, and in 1981, "on a very, very small amount of money", they founded Cheek by Jowl.

Twenty-three years on, the company is busy touring the world withOthello - they began in Lille in March and will finish in New York in October, having been to Italy, Turkey, Russia, Portugal, Australia, Poland, Shanghai and the Czech Republic en route, as well as around the UK. Donnellan's next project is the British premiere of Nikolai Erdman's 1925 play The Mandate at the National Theatre, which Donnellan is not just directing but has also translated. Banned in Russia till the 1990s, but since then a mainstay on the Moscow theatre scene, it is set in a communal flat, whose bourgeois occupants, fearing the Communists, are desperately pretending to be proletarian. "Instead of a vicar in the wardrobe," he says, "there's a maid in a posh dress whom they mistake for the Grand Duchess Anastasia and lock in a chest. It's an extraordinary mixture of Joe Orton and Barbara Windsor and political satire. And it's incredibly funny."

Then it's back to Russia for a production of Chekhov's Three Sisters with the Russian Theatre Confederation, the company from which his regular nucleus of Russian actors is drawn - "a kind of Cheek by Jowlski". First off they'll be going as far as possible from Moscow to prepare (they'd been promised a fortnight at Tolstoy's country estate, but it transpired there were no bathrooms). He's also been asked by the Maly to go to Surgut, in Siberia, in December, but is fearful of the cold. "In any case," he says, by way of an excuse, "I've already worked in some grim places like Yekaterinburg and Chelyabinsk."

But for all the time Donnellan now spends in Russia, he is keen that he shouldn't be perceived as turning his back on British theatre, which he feels is on a roll. Having missed the doom-mongering that followed the rash of West End closures earlier this summer, he is "amazed how positive the theatre atmosphere is in London now. I've just done two weeks of auditions at the National and the talent, the exuberance and hope is extraordinary. I also have connections with the RSC, and everything there seems to have changed so much for the better. It's like coming back to a different country.

"People really admire British theatre all over the world," he continues. "It's an art form we excel at, like sculpture and architecture, and I very often feel ambassadorial. But taking plays to foreign cultures is always very strange, especially when we bring things to London. To tour into your own home city, which I've done with Boris Godunov and The Winter's Tale, both in Russian, and Le Cid, which I did in Avignon in French, and see your work surtitled - that's extraordinary." Still, he reckons it's taught him a lot about translation, and how it is more often the simplicity than the complexity of language that is lost. Which is why acting matters so much.

Ultimately, he believes, theatre can have an "incredibly profound effect" on its audience, just as it had on him. "Seeing something great when you're young, you can be completely synapsed for the rest of your life. The word 'spiritual' is so vexed, but art can provide a sort of profound interconnection with the rest of humanity that gives you a sense of hope and of opening doors. Every now and then somebody will come up to me and say they've seen something I've done and it's made an incredible impression on them. It's a great privilege to be part of that process, to use the gifts that you've been given and pass them on."