She was crowned the next Darcey Bussell long before Britain's last prima ballerina had hung up her pointe shoes. Yet it will be only tomorrow night, when the curtain rises on Alice's Adventures in Wonderland, that Lauren Cuthbertson can truly lay claim to her anointment.
Cuthbertson, who is the Royal Ballet's only female British principal, will dance on to the famous Covent Garden stage as Alice, a role created specially for her in the ballet company's first full-length classical ballet for 20 years. She is the first dancer since Bussell to open a ballet written for her and can hardly believe her luck.
"From the bottom of my heart, it's the biggest gift that a dancer can receive from anyone... I know that quite easily this could never happen again," she tells me breathlessly, still coming down from the high of Friday morning's dress rehearsal.
It is seven years since Cuthbertson, 26, debuted as Juliet in her first starring role, and three since she was made a principal, but the butcher's daughter from Devon thinks she has yet to peak. "Despite a fairly rapid rise, my progress has felt quite slow. I plateaued and went back in the queue. In some ways, I feel as if I'm only just coming to my potential," she admits. Given that it is between 27 and 34 that a female dancer is widely thought to excel – "because your technically best years match your emotionally best ones" – she may have timed it just right, more by luck, as it happens, than by design. Dancing Alice will complete Cuthbertson's astonishing comeback from an illness that left her unable to make it out of her bed and wondering if she would ever dance again.
Her body simply shut down months after her accession to principal; her doctors diagnosed glandular fever and "weeks and weeks would go by in a complete fog". Looking back, she says: "I had moments at home when I just thought, 'This could be it. It could so easily be it.' How do you get back when your body isn't functioning? My brain wasn't functioning; my eyes weren't functioning."
She spent much of 2009 and 2010 out of action, missing juicy part after juicy part. Rehabilitation was slow: she describes taking her exercise in two-minute bursts. But she made it and, luckily for the sell-out audience for tomorrow night's gala performance, she feels "comfortable enough to say I'm better". There are limitations, but she says: "I've learnt how to deal with it. I still have a couple of days here and there where nothing is co-ordinating, nothing is functioning, but I'm dealing with it. I don't want to be known as the girl-who-might-not-turn-up-to-a-show. I'm professional. I handle it."
Alice will be her very own Black Swan moment. Like Nina, Natalie Portman's character in the Oscar-nominated film, Cuthbertson has waited years for such an opportunity. Expanding on the similarities, she adds: "It's this talked-about thing and I'm right at the centre. Alice is my first principal full-length ballet I've ever been given first night for. For me, the experience of having something created is so rare, it's like gold dust."
But there the parallels with Nina end. Like many dancers, she cringes at the clichéd liberties that Black Swan's director, Darren Aronofsky, took with her world. For what it's worth, she wouldn't give Portman the best actress Oscar tonight. "Not for this part." She scoffs that Portman was called a "prima ballerina" when she won her Bafta; barely any of the supposedly top dancers merit the accolade, let alone an actress. She explains: "A ballerina is very special. Not everyone here is a ballerina, even if you're with the Royal Ballet. When one of my dearest and oldest teachers said to me after a performance, 'You were a ballerina tonight; you've become a ballerina,' for me that was not so much a compliment but almost a crowning of a rare title."
There's no denying, however, that she shares the slender physique of Portman's character, even if she doesn't share her eating habits (the only food Nina eats during the film is half a grapefruit and a lick of icing). Cuthbertson doesn't shy away from discussing her frame, conscious that a dancer gets criticised as much for her build as her technical ability: witness the storm that erupted when the New York Times' dance critic accused Jennifer Ringer, cast as the Nutcracker's Sugar Plum Fairy, of eating "one sugar plum too many".
"I feel sad for the girl," she says. "She's the victim of a massive debate within the world, not just the ballet world. The way society looks on people now is very judgemental." Yet judgements clearly rub off, and the slip-of-a-star sitting cross-legged on the sofa opposite me, nibbling a fruit salad, adds: "I feel quite strongly that to be your best you have to feel your best. That's hard for anyone and it's hard for a dancer. I was bigger a few years ago, but I'm much happier being slighter. I feel less self-conscious and I feel better doing pas de deux. But that doesn't mean I get dizzy all the time or just eat grapefruit. I have to swim; I have to do yoga; I have to do pilates, all on top of my work."
For proof of the transformative powers of ballet, you need look no further than her unlikely Alice co-star: the character actor Simon Russell Beale. Picked by Christopher Wheeldon, the ballet's choreographer, to dance the Duchess, Russell Beale has lost three stone since taking up his new art. As for what the actor brings to the Royal Ballet, Cuthbertson says he's "wonderful, like a breath of fresh air. It's really lovely to have him there".
Just don't expect the 49-year-old actor to be partnering her: Dame Monica Mason, the company's director, might like to chop and change her principals' partners, but Beale would be a step – even one of his "delicate" dance steps – too far.
As for the Bussell comparisons, the young pretender insists they are "totally different". But if she nails the reviews tomorrow night, any differences may become immaterial.