Charlie Cox: Star turn

I'm watching a preview of the Harold Pinter double bill at the Comedy Theatre on the night before I meet Hollywood's newest star, Charlie Cox, when I encounter his fan club in the row behind me. The girls gasp collectively at how good-looking he is, especially at the end of The Collection, when he strips off to a pair of tight white boxer shorts.

The English public school-educated 25-year-old is not only converting teenagers to Pinter, however; he also holds his own with his more experienced co-stars, Timothy West, Richard Coyle and Gina McKee.

The young star has just played the lead in the blockbuster family film Stardust, alongside such Hollywood luminaries as Michelle Pfeiffer, Robert de Niro, Sienna Miller and Claire Danes. Cox's character was the earnest, genuine Tristan, who transforms from boy to man on his quest for true love. In real life, too, the actor is growing up fast as he finds himself, right at the beginning of his career, rubbing shoulders with the acting elite. Although he had picked up some good roles – performing opposite Al Pacino in The Merchant of Venice and in Casanova alongside Heath Ledger – the actor was relatively unknown until a few months ago. Nowadays Cox, with his boyish, wide-eyed good looks, gets recognised wherever he goes.

When we meet the morning after the Pinter previews, the actor is cleaning his teeth in his dressing room at the Comedy Theatre. As he welcomes me inside, he takes off his porkpie hat to reveal a mass of bouncing, newly cut hair and clear brown eyes. His dressing room, which has the feel of a miniature flat, is nevertheless smaller than those of the other three members of the cast, because, he says as if he is still at boarding school, he is "the new boy".

His costumes for the character Bill – who in The Collection is accused by a husband (Coyle) of having a one-night stand with a married woman (McKee), despite being in a gay relationship with Harry (West) – are hanging tidily over a camp bed. There is a Just For Today meditation book on the table – a 12-step recovery tool – because the actor no longer drinks. He has already begun pinning things neatly to the white walls, to create a collage that will document his four-month run in the play. So far it includes a line of fizzy vitamin C sachets, a Nurofen Cold & Flu packet, even three different Starbucks coffee cup sizes. He points out everything to me – "I will remember the bad cold I had at the beginning of the run" – but it is only day four. He is still warming up in his first proper job on a West End stage. "I am far out of my comfort zone. I am trying to keep up with actors who are consistently brilliant, not like me, this Disney kid Cox from Stardust."

Cox lives in World's End, Chelsea, above an art gallery, with his best friend, Ned, and dog, Ralph. He speaks with passion and maturity about his job, and has a calm presence as well as heaps of energy, which he uses both positively and negatively. "I am incredibly self-deprecating. It stems from self-doubt. With every job I watch, I can't find peace with what I've done. It's never good enough in my mind. I will never be happy if I'm in that mindset, unless I get a review that starts: 'once in a generation'," he says, laughing. "Fame terrifies me. I can say that with honesty. You're terrified that, when people know the real you, they won't like you."

The actor was born in 1982 and grew up in East Sussex with his publisher father, Andrew, his mother, Trisha, and his older brother, Toby. He also has three much older half-siblings, Ollie, Emma and Zoë, who were all leaving home by the time he was born. At the age of eight, he was sent to a local prep school and then to Sherborne School in Dorset. He won the school's Gerald Pitman Award for Drama twice, before leaving school for London at the age of 18.

He got a supporting role in the film Dot the I opposite Gael Garcia Bernal, before starting at the Bristol Old Vic Theatre School at 19 years old. It was a miserable experience. "They start picking holes and I took it all too personally." Auditioning for roles was banned while pupils were still at the school, but after his first year he secretly auditioned for Pacino's The Merchant of Venice. "I remember feeling really panicked. I was meant to have learnt to play the recorder for the class nativity play when I got the call from my agent telling me I'd got the role. The next thing I knew I was hanging out in Luxembourg with one of my idols. Deep down I knew I'd never go back to Bristol. To slot back into my class after that would have been entirely weird."

He then played a warrior in an unwatchable Spanish film, Tirante el Blanco. "To call it a flop is an understatement. The film made no sense. It hadn't been translated properly. I wasn't even invited to the premiere." He returned to the UK to perform for no wages in 'Tis Pity She's a Whore to packed houses at Southwark Playhouse. The production, directed by Edward Dick, received rave reviews. "None of us got paid for it but it ended up being one of the shows to see in London."

This was the first time that the actor had a difficult decision to make, as he had already been offered a role in a big feature film when the Pinter play came up. "It really threw a spanner in the works because there is a pressure to continue to do films. If you disappear for a little while, they just lose interest. But if I want to be still acting when I'm older, the Pinter play is the kind of work I need to be attached to. The theatre is where I'm learning my trade," says Cox. "In Tim's [West] day he did years of rep theatre. Today we are in a manic rush to be rich and famous. None of us young stars has had time to learn our trade. There is a horrible misconception that you can either act or not. But experience is everything."

It is a challenge for Cox, playing a lead role in The Collection – one of the two rarely performed Pinter plays, the other being The Lover, which are being revived at the Comedy Theatre under the direction of Jamie Lloyd, who recently directed The Caretaker for Sheffield Theatres. "Harold [Pinter] has been involved in the production, but he hasn't told us whether my character Bill really did sleep with Stella or not. He is the only one who really knows. Gina [McKee] and I made a decision that we think helps us, but we are keeping that decision a secret." Bill is a million miles away from his Stardust role of Tristan, who wore his heart on his sleeve. "What is certain about my character Bill is that he lies all the time. Whether Bill did it or not, he still gives different versions of the story. He is a bit of a spoilt brat who doesn't think of what other people want. He just wants a bit of a drama. He craves power and manipulates people for his own amusement. He annoys Harry for no reason at all other than to entertain himself."

For Cox, who has been living out of a suitcase for so long, starring in the West End allows him something of a normal routine. He can walk his dog and hang out with the small group of friends whom he has known since childhood. Fame has not changed him, and he doubts it ever will. None of the older actors hasever sat him down for a pep talk either, but Pacino offered him some words of wisdom. "Al said, 'You're not an actor until you've got a leather jacket.' I took it very seriously and asked my parents to buy me this brown leather jacket for my 21st birthday. It's worn really well, hasn't it? Then Al rang me on the day to wish me happy birthday while I was in the middle of having a small party. Answering the phone to him was one of the most bizarre things that has ever happened to me."

Now Cox has another offer to star with Pacino, in Enclosure, a black comedy about a Jewish family. He has already finished filming Stone of Destiny, based on a true story, in which he plays Ian Hamilton, a committed Scottish nationalist who in the 1950s led a raid on Westminster Abbey to bring the Stone of Scone back to Scotland. The actor talks about his career with the excitement of somebody who is living his dream. In promotional TV interviews for Stardust he looked almost startled, but since he's been at home he seems to be more at ease. "It's so easy to become obsessed with the film industry and recognition that we can forget that we are not saving the world. We are just actors trying to entertain people. Doing this play, in front of a live audience, has reminded me of that."

'The Lover' and 'The Collection' run at the Comedy Theatre, London SW1 (0870 060 6637) to 3 May