Stage lights, says Sergei Polunin, can conceal as much as they illuminate. Perhaps it's just as well, because among this youthful Ukrainian's ventures into body art beyond ballet is a simulation of tiger scratches on his torso. "Nobody really noticed my tattoos," he remarks. "I put Sellotape or pancake make-up over them, but you'd be surprised how much you can't see when the lights hit."
What you can see of Polunin, the Royal Ballet's youngest principal dancer, is mightily impressive. Long-limbed, with a radiant openness about his upper body, a spacious musicality and an apparently weightless, stratospheric jump, at only 21 he's a persuasive candidate to be British ballet's biggest hope. One bedazzled critic, reviewing him in Rhapsody earlier this year, even declared him "better than Baryshnikov" – praise indeed.
This season is packed with vital landmarks and debuts for him: tonight, he makes his debut in Manon as Des Grieux, the luxury-seeking heroine's unfortunate lover. Soon there's his first Romeo in Kenneth MacMillan's Romeo and Juliet and an international cinecast of The Sleeping Beauty in which he is the Prince.
Polunin looks like a young man in a hurry, but in fact he is lucky to be alive. Aged eight, he contracted pneumonia; one of his lungs stopped working and the local hospital sent him home still ill after six weeks. The condition lasted a year. "My mum tried everything," Polunin remembers. "Eventually, I ended up seeing this guy who heals with his hands." After 10 sessions, by hook, crook or miracle, he was better.
He was born in Kherson, close to the Black Sea in Ukraine, where initially he joined a sports school to learn gymnastics. Pneumonia ended that: "I couldn't come back to gymnastics because the floors were too dusty for my health." The alternative was ballet. "Some of my friends were going to dancing school and, when one of them was auditioning for a ballet school in Kiev, my mother saw an opportunity for me to do that, so we could move to a bigger, better city.
"I'd always been one of the best in my gymnastics school, so I transferred to trying to be the best dancer, without knowing anything about ballet. I learned it as a routine. And even in Kherson, which had nothing like a ballet company, they respected dancers. It was so rare for a boy to be a dancer that everyone was impressed, even street kids."
Kherson, he adds, was desperately poor: "Everyone was living in the same poverty and there was no hot water or electricity after 6pm. I had pocket money for good marks, but at some point I had to give it away for food. We moved to Kiev with $10 in my mum's pocket; that was all. My dad went to work as a builder in Portugal and my grandmother went to Greece to support my mum and me." He and his mother lived in one room for four years in Kiev.
Next Sergei auditioned for the Vaganova Academy in St Petersburg. It wasn't for him, nor he for it. "They were quite excited when they saw me dance but when they heard I was Ukrainian, not Russian, they backed off," he says. He speculates that this might be due to the school's funding set-up. "Besides, the whole city felt wrong for me. It was very cold and, in St Petersburg general, schooling is more important than dancing. I hated school." He is dyslexic, he says: "Homework was torture."
Now his mother suggested London and the Royal Ballet School. His father called an acquaintance in the UK who told them how to apply. Sergei was soon invited to audition but when the letter of acceptance arrived, it was in English and they could not understand it. "We thought it said we would have to pay £32,000 a year in fees, so we decided to forget the whole thing."
If his ballet teacher's dog had not played with another dog during a walk soon afterwards, he might not be here now. The two dog owners talked and became friends. "This friend knew English, looked at our letter and said: 'no, you need a sponsor, but you don't need to pay anything yourself'." The same friend put the Polunins in touch with UK contacts to help find Sergei sponsorship from the Nureyev Foundation.
Aged 13, he arrived at the Royal Ballet's junior school, White Lodge, in Richmond Park. "I'd read the Harry Potter books," he laughs, "and it felt just like that!" His fate seemed assured when he won the prestigious Prix de Lausanne in 2006; and at last he entered the Royal Ballet itself, having graduated from its school two years ahead of his age group.
Now he's relishing the high demands of his biggest season so far. Des Grieux is a big challenge, he adds, for peculiar reasons: "I like strong characters, big steps and jumps. This role is a weak character, he's insecure and it's all adagio! It's very pure. I think my dancing comes over as a bit wild, even if I'm thinking 'pure'. The challenge is to make him interesting, without putting across the wrong type of character."
His Manon is Lauren Cuthbertson; together they created the leading roles in Christopher Wheeldon's Alice's Adventures in Wonderland earlier this year and their partnership has attracted much enthusiasm. "I think our lines complement each other – we both look quite long," Polunin suggests. "And she's very spontaneous, which makes it exciting to dance with her."
Nevertheless, there's a sense that Polunin is champing at the bit. He's had invitations to make guest appearances with American Ballet Theatre and in Russia, and wasn't pleased to find that his Royal Ballet duties would not allow him to go. But he managed some moonlighting closer to home: last month he danced in The Phantom of the Opera when it was cinecast to celebrate its 25th anniversary.
His dream roles, he says, are "manly" characters that require immense drama; long-term, he has his eye on two MacMillan masterpieces, Mayerling's crazed Prince Rudolf, and the dark and devastating The Judas Tree. But he loves dancing Albrecht in Giselle: "The second act is so cleverly choreographed that when you're supposed to be at the point of death, you feel you really are."
He's hungry for life and experience. "I'm not good!" he declares. "I don't do many classes. Sometimes I don't eat all day, then have four meals between 8pm and 4am. I go to bed really late – if I just sleep I won't have a life outside ballet. And I have this idea to open a tattoo place. I'd like to create something classy, with open windows, maybe some celebrities coming in..." He is not joking. "It'll be 50-50 with this American guy who's a former gangster and learned tattooing in jail. I'm fascinated by that life. Once I went back to my old city and saw my best friend from childhood walking around with a gang, looking cool. I think I missed out by never having that street life doing stupid things."
There's another tattoo on his lower back, he says, in glass letters: "It represents my memories being washed away by rain." His parents broke up when he was 14. "I was very upset," he says. "After that I decided I was never going to think about anything bad again."
His life is literally inked into his body. Perhaps it is inked likewise into the power of his dancing.
Sergei Polunin dances Des Grieux in 'Manon' on 8 and 15 November, Royal Opera House (020 7304 4000)