Twenty-seven-year-old Polley can take a joke. "Sam and Wim are just like that, " she says. "I can't imagine two more interesting people to spend time around. Wim is incapable of being snotty and Sam's incapable of being anything other than really wise."

She can see the funny side of spurning Hollywood, as she has done.

She's so serious about all things Canadian that she dropped out of Cameron Crowe's $60m Almost Famous . . . causing Brad Pitt to withdraw too . . . so that she could star in a $1.5m Canadian independent movie Rules of Enclosure.

Kate Hudson took her place and won an Oscar in the role of Penny Lane.

The daughter of actors, she made her debut at the age of four in Disney's One Magic Christmas. The popular CBC television series Road to Avonlea turned her into 'Canada's Sweetheart'. By 12 she was independently wealthy. Upset by Disney's Americanisation of the series, she insisted on her character being written out of the show's plot.

When she was invited by Disney to appear at a Children's Awards Show in Washington DC, she turned up wearing a peace symbol in protest against the Gulf War. By 14 she'd left home to live with a 34-year-old man. She joined the New Democratic Party and lost several teeth to riot police at a protest rally in Toronto. She returned to movies at 18 with a stand-out performance as a teenage girl injured in a school bus tragedy in Atom Egoyan's The Sweet Hereafter. After a number of relationships with older men . . .

including director Michael Winterbottom . . . she's now married to film editor David Wharnsby.

Small, blonde and with blue eyes, Polley admires Shepard for the way he writes from character rather than to put across an idea. "He's not trying to say anything and I think ultimately that's why he says so much. Don't Come Knocking has become absurdly personal for me on a whole lot of levels that I actually probably don't want to talk about.

"One thing I would talk about is that my mum was obsessed with Sam Shepard. Her dream would have been to have been in a film with him. And there's this crazy moment where I was doing a scene and I'm putting a photo of my character's mother beside a photo of Sam's character, and I suddenly realised, Oh my mum is in a movie with Sam Shepard. It really got to me."

Polley's mother Diane died from cancer just after her 11th birthday. "I try to veer away from drawing on my life when I'm acting but sometimes it's unavoidable, " she says. I don't literally use things I've experienced but I think that subconsciously you're always using things from your life. You find yourself in the middle of a scene acting something out of your life that you never expected."

Polley, who starred with Julie Christie in Isabel Coixet's Goya-award winning The Secret Life of Words . . . she plays a nurse who travels out to a rig to care for a burned oil man, Tim Robbins . . . has now cast Christie as the elderly wife of a philanderer in her directorial debut, Away From Her which she is currently filming in Toronto. "Julie has become like a surrogate mother to me, " she says.