She says Thirteen has caught on in a way she never expected, 'because it's a tiny examination of family life'. All the more startling is that the film's in-your-face story of the lives of two tattoo-loving 13-year-old girls wasn't really Hunter's to begin with, yet she built up her character to the extent that her recovering alcoholic divorcee, who is struggling to raise her kids on very little money, becomes the heart of the film. And this, when Hunter has never been a mother herself.

'I thought the screenplay had a real authenticity,' she says. 'It's a kind of shocking expose of how we can tell ourselves a lie - a portrait of an intelligent woman who wants to understand her daughter, but treats her only as a friend. Being a friend to a child is not a bad thing, but she's also got to be a parent. I think many people can relate to this. 'Raising a kid is really difficult, according to all my friends - and according to my mum,' she says.

Hunter is famously choosy about roles, but nudity is not one of her taboos. 'Bad scripts are,' she quips. She readily took on nude scenes in Thirteen. 'Somehow it's not an issue for me. The nudity I've done has been called for. When I first read the scene, Catherine had me holding a pillow to shield my nakedness from my boyfriend. But it tells a lot more about their relationship if she doesn't even think about nudity. It's not the thing that's going on between them.'

For this experienced, worldly actress, the really daunting prospect was working with two knowing 13-year-olds. Tracy is played by US television starlet Evan Rachel Wood. Her corrupting influence, Evie, is played by the film's co-writer, Nikki Reed, on whose experiences the story is based. 'Those girls wore me out,' Hunter says. 'I was very impressed with their enthusiasm for life - even though I felt that Catherine and I have a great enthusiasm for life, too. But I'm 45, and this is who I am now.

'In many ways they remind me of me at 13, in their ability to shift from one persona to another, but they know more than I did and they are less naive. At the same time, they're still children, and that's confusing for me and for everyone around them. Often I would feel that I was dealing with adults, because of the sophistication with which they can look at life and how poised they were in situations that I would have been overwhelmed by at their age. I think it's a more challenging place to be a teenager now, with the internet, TV, high-fashion magazines and tabloids that assault you when you go to the grocery store. All that has really accelerated since I was 13.'

Hunter is a powerhouse performer, who wrings every ounce of humanity and emotion from her characters. So, you might think that meeting her in the flesh would be daunting, that she'd be neurotic or unable to discuss her work. But she is smart and articulate - reminiscent of a Jodie Foster, although more risque.

For our interview at the Deauville Film Festival, Hunter has flung off her heels and is curled up on a hotel sofa. She wears little makeup, and her long blonde streaked hair falls in a tumble of curls, which frame her frequently huge smile. She seems happy, clearly ecstatic at the turn her career is taking. But she admits it's the luck of the draw.

Her film career took off when Joel and Ethan Coen saw her in a Broadway production of Crimes Of The Heart. A few years later, when sharing a house with the Coens and her friend, actress Frances McDormand (who married Joel, and remains Hunter's close friend) the Coens wrote Raising Arizona for her. The 1987 film became a huge hit. That year, Hunter also won rave reviews for her portrayal of a hard-nosed TV producer in Broadcast News, a role she had to convince director James L. Brooks she was capable of playing. He was, of course, convinced, and went on to offer her the female lead in As Good As It Gets - the role for which Helen Hunt won an Oscar after Hunter turned it down. 'I would have loved to have worked with Jim a second time, but it just didn't work out. I've turned down lots of movies, and it's meant to be that way.'

Her inevitable Oscar win came in 1994 for The Piano, directed by her now good friend Jane Campion, who was convinced by Hunter's persistence, and by her piano playing. (She played her own music in the film.) In the same year, she was nominated for her role as an investigative secretary in The Firm. She has also starred in Foster's Home For The Holidays, Copycat and Jesus' Son directed by Campion's New Zealand colleague Alison Maclean.

'Probably the only movie I've ever made that was overtly commercial was Always with Steven Spielberg,' she says. 'But it's the others that have been the great successes in my career. Raising Arizona ended up making a lot of money. The Piano and Broadcast News were both small, but caught on.'

In the past three years, Hunter has separated from her husband of five years, cinematographer Janusz Kaminski, and moved to New York, where she lives in downtown Manhattan, not far from where her theatre career began. 'I like New York,' she says. 'There is such a wonderful mix of cultures and there's so much life on the streets.'

Born in rural Georgia, Hunter grew up driving a tractor on a farm, but always had strong creative urges. 'I studied piano from the age of nine,' she says. 'I convinced my parents to give me lessons because I loved it so much, and I've played all my life.' She moved into acting early, in school plays. At 15, she was offered a four-month stint in a repertory company in New York and went on to study drama in Pittsburgh before her 1981 off-Broadway debut.

She is hoping to appear this year in London's West End, reprising her performance in The Bog Of Cats, a retelling of Medea by Irish playwright Marina Carr.

'In movies, I'm not a typical leading lady. Nor am I a typical character actress,' she says. 'Even leading parts I've played have been particular women, not anonymous types. And that's why I continue to be involved in the theatre, because the theatre is about the particular, never about the generic. And obviously I'm attracted to that - as it is attracted to me.'