She’s going great guns in Hollywood but Sophia Myles is a home girl at heart, says Sebastian Shakespeare

Sophia Myles is bunched up in an armchair in a Charlotte Street Hotel drawing room, squirming with embarrassment. What could be more embarrassing for this 25-year-old vicar’s daughter from Isleworth than appearing naked on screen, as she does in her new film Art School Confidential? She winces, grimaces, covers her eyes with her hands and peers at me through her fingers. And all because I asked a prudent question: which co-star is the better kisser, Johnny Depp or Rufus Sewell?

‘Oooh God,’ she says. ‘OK. Right. Rufus is one of my really good mates now.’ Long pause. ‘Well that is a really good question, Tatler, a really good question.’ Another long pause. ‘Um’… She begins to blush. ‘I feel like, I don’t know. Maybe Johnny Depp.’ She is so anxious not to offend anyone that every opinion is qualified by a caveat. Now she has laid her tongue on the line she spends the rest of our interview fretting: ‘Rufus is going to kill me.’

When it comes to her own shortcomings she is disarmingly candid and down-to-earth. She confesses she has ‘a spot coming on’ and corrects me about her A-levels: she got an A, a B and a C, not three As as the cheap print have it. She could so easily have let that slur stand.

Has the time come for the actress Vanity Fair once tipped as the Next Big Thing? After starring as Lady Penelope in Thunderbirds, it is all systems go. She has two films out this spring, Tristan & Isolde (with Sewell and James Franco) and Art School Confidential (opposite John Malkovich and Anjelica Huston). She is also to appear as 18th-century Frenchwoman Madame de Pompadour in Doctor Who with David Tennant, her current beau.

She arrives punctually, dressed in Seven jeans (Joseph on Westbourne Grove), a white jacket (Joseph again), black top (Banana Republic), brown leather boots (Hobbs) and a flat cap (a freebie from LA). ‘I think you have to make sure you scrub up well when you go out’, she says. ‘Otherwise, I’m a bit of a slob at home. I am make-up free.’

Tristan is an epic weepie in which Sophia has to choose between Tristan (Franco) and Lord Marke (Sewell). ‘James Franco is Mr Method, verv intense’, she says. ‘He scoured the globe for every single copy of the original story whereas I sat with a pint of Guinness and my script.

‘This job was very demanding, one of the tough ones. It was so cold and the scenes in the water and the fights were physically very challenging. Emotionally you have to spend the best part of a day bawling your eyes out. It does drain you. I think as a whole it’s one of the best things I’ve done. That and Mansfield Park.’

Happily, Sewell and Bronagh Gallagher provided light relief. ‘We didn’t know each other before the film. The three of us had a right laugh. I’ve got great friendships that are one-to-one, but up to that point I can safely say that I have never been part of a posse of mates. That was what I enjoyed most about it. During the love scenes I kept giggling. Rufus and I had become so friendly before we shot our love scenes, we spent most of the time trying not to laugh.’

In Art School Confidential she goes naked, whereas for Tristan she had a no-nudity clause. Why the change of heart? ‘I wasn’t ready. More importantly, I didn’t feel it was necessary. l don’t think by the lack of seeing one of my arse cheeks, the film has been any less appealing. It’s not going to change the essence of the story. In Art School Confidential the context is so different – I play a model in John Malkovich’s line-drawing class. But if there is going to be nudity in a film, I would rather do it myself than use my body double. If they use one, they can go and do a day’s shooting, you don’t know what they’re doing and people still think it’s you.’

Her looks have inspired comparisons with Kate Winslet, though she attributes her oval face and blue eyes to her paternal Russian grandmother. Sophia was born in 1980, when her father was vicar of St George’s, Campden Hill Square, and was raised in Notting Hill. She was talent-spotted by Oscar-winning screenwriter Julian Fellowes in a school play and cast, aged 16, in a BBC version of The Prince and the Pauper as Lady Jane Grey. ‘I just completely fell hook, line and sinker in love with the industry as soon as I stepped on the film set. There was no turning back. I was on a mission and still am.’

She juggled her A-levels with acting and appeared in TV dramas such as Big Women and OliverTwist, on which she bonded with Keira Knightley, but decided against going to Cambridge University to study philosophy. ‘I got in, but would have had to re-sit an A-level. I thought, “Hang on, I can go and get paid money to make Mansfield Park and work with Harold Pinter.”‘

After 18 months of unemployment between OliverTwist and Nicholas Nickleby – ‘the dark time between two Dickensian tragedies’ – the work picked up. She played a tomboy vampire in Underworld and Johnny Depp’s wife in From Hell. Beating Sophie Dahl and Rosamund Pike to the role of Lady Penelope was a turning point, despite Thunderbirds‘s poor critical reception.

Now she is more in demand than ever. She has just recorded her first American TV miniseries and is about to go into rehearsal for a film directed by Young Adam‘s David Mackenzie, co-starring James Bell.

Her role models? ‘I have a lot of admiration for people like Reese Witherspoon, who is not only very talented but very funny, and has also maintained a family and kept her private life very private.’ Sophia’s own private life has caused an occasional flurry of media interest ever since she dated Charles Dance, whom she met on Nicholas Nickleby. ‘I’m in a great place now. I don’t know what will happen in six months or a year. You don’t know what’s coming your way.’ She wants to have children, ‘definitely by 30’, but doesn’t see herself taking a baby onto a film set.

Home is a £500,000 flat in Queen’s Park, and she relaxes by pottering, cooking (‘I can make a mean spaghetti bolognese’) and listening to guitar music (James Taylor, Tracy Chapman). She wouldn’t want to move to LA full-time because she would miss culture and the seasons. Unlike Sienna Miller, say, she is not often seen on the party circuit. ‘I know networking is a huge part of my job but I’m quite shy about it. It’s not in my nature to work the room.’

Being invited to appear on Doctor Who was ‘like being called to jury service. You can’t say no to Doctor Who. Nor, it seems, could she say no to its star, David Tennant – the two have been an item ever since. ‘The Pink Paper recently voted David the sexiest man in the universe,’ she says. ‘I’d definitely agree. I will go and buy one of the Doctor Who action figures and carry it in my handbag. I’m very pissed off they are not making a Madame De Pompadour doll, though I have had words with the producers about it.’