The new Julie Christie

With a flick of the hair and a steely stare, it felt for a moment as if I'd stepped back 37 years to interview an unknown ex-model called Julie Christie, all perfect porcelain skin and delicate features, preparing to stun the world with her dramatic performance in Dr Zhivago.

The facial resemblance is uncanny, as is the extraordinary confidence in one so young and, to be frank, so inexperienced. But 17-year-old schoolgirl Keira Knightley seems remarkably unfazed. She's taking on Lara, one of the great female roles in literature - one inextricably linked to the divine Christie who was then a positively adult 24 - and once it's all over, she'll be jetting off to Hollywood to star with Johnny Depp in a £60 million pirate adventure. It's all a far cry from A-levels in Teddington.

"It's like a dream come true but I'm not caught up with the hype surrounding it. I've always loved the film and Julie Christie was great but, nearly four decades on, it deserves another take."

The £7 million remake is the jewel in the crown of ITV's winter season and is liberally sprinkled with graphic sex scenes, written by Andrew Davies, the man behind salacious lesbian drama Tipping the Velvet. Keira will romp with fellow newcomer Hans Matheson, 26, who plays Zhivago, or Hollywood heavyweight Sam Neill who stars as Lara's middle-aged seducer Victor Komarovsky. But not even rolling around semi-naked with a superstar the age of her father uneases her.

"I don't have a problem doing scenes like that if a script requires it and this does," she says. "I was a bit nervous in the first one but it's a great way to break the ice. We were two weeks into shooting when Hans and I had to do one and we both went off into hysterics."

Clearly if Davies's adaptation of Boris Pasternak's Russian Revolution classic affects sensibilities as much as his last work, the pressure on Keira will be huge. Fortunately, she has a cool head on young shoulders. "I did expect to go back to school in September but then two films came along and I decided I shouldn't," she says. "The opportunities aren't going to last forever so you have to make the most of them. I will go back to my education when I've got this acting lark out of my system. Maybe I'll go and train to do something proper."

That somehow seems unlikely. Having excelled in this year's football comedy Bend It Like Beckham, she has just finished filming Love Actually with Emma Thompson and Hugh Grant. Surely no one in their right mind would turn down the likes of Johnny Depp to sit in a sixth-form tutorial.

"I never imagined I would be in this position, reprising such a famous role - it was a shock when I got the part. My parents are a bit bemused by the whole thing, especially my dad because he fancied Julie Christie in the film and he can't get his head around the fact that I'm playing the part now."

The daughter of award-winning playwright and novelist Sharman Macdonald and actor Will Knightley, she caught the performing bug early. At 14, she was chosen to play the decoy queen Sabe in Star Wars: Episode One - The Phantom Menace alongside Natalie Portman and Ewan McGregor.

But this is her biggest challenge, made even harder for having to plough through Pasternak's huge novel. "I'm dyslexic. Dr Zhivago is not the easiest Russian classic to get through but I persevered and read it four times."

Keira has now returned to her family in Teddington before jetting off to start Pirates of the Caribbean. "I can't wait to meet Johnny,' she gushes. "I hear he's adorable. But I've made a pact with myself not to talk about it, though I can't help myself as I'm so excited.

"I'm sure this wonderfully unreal existence will all fall apart at some point. By the time I'm 20, it will either have disappeared or it will be trundling along nicely. But then I'm not meant to be thinking all those sorts of things yet. I mean, I'm only a teenager."

Dr Zhivago is on ITV on 24 November.