Natalie Dormer on playing England's naughtiest queens

The real beauty of being an actor is the huge cross-section of projects you can work on,' says Natalie Dormer. And she should know. This year alone, Natalie has spent six months playing a sensual turn-of-the-century Viennese woman in

Natalie, it must be said, is not. She has wide, slanting pale blue eyes, waves of ash-blonde hair and looks like a member of the House of Elrond. These ethereal features have led her to be cast in a succession of refined costume roles, most notably as Anne Boleyn in The Tudors, the wildly successful TV series, and latterly as Elizabeth Bowes-Lyon in W.E. The strangely titled film, which was co-written by Madonna with her friend Alek Keshishian, the director of In Bed With Madonna, is a sympathetic retelling of Wallis Simpson's story in parallel with a modern love story.

Natalie admits that taking on the role of the Queen Mother was a daunting prospect. 'Everyone remembers her as the national treasure, with white fluffy hair and the lavender coat,' she says. 'There's not a lot of footage of her in the 1930s, though I really tried to find it.' She ended up asking for tips from actor Michael Sheen, lauded for his cinematic portrayals of Tony Blair, David Frost and Brian Clough, who advised her to try to convey the spirit of the woman rather than her physical likeness. 'Hopefully William and Harry won't be too pissed off with me,' she says, although you rather suspect they won't be thrilled, especially as their great-grandmother is the villain of the piece, famously hostile to Wallis, whom she blamed for George VI's early death, and refusing to speak to her after the abdication until the Duke of Windsor's funeral in 1972. (It is telling that although permission was requested to shoot at Buckingham Palace, all filming took place on National Trust properties.)

Anyway, what we're really interested in is not the Royal Family but her Madgesty. What is she like as a director? Unsurprisingly, absolutely clear about what she wants, it seems. In fact, her controlling behaviour has already caused actress Margo Stilley to storm off the set.

'Madonna is nothing but very direct and specific,' says Natalie carefully. 'This is one woman's gorgeous vision and you go on set knowing that's what you're doing.' So no arguing about your motivation then? Natalie bursts into roars of ironic laughter. She certainly found it strange to hang out with one of the most famous women in the world. 'As a child, I was prancing around in my mother's high heels and a ra-ra skirt singing 'Material Girl' into my hairbrush. She was one of my idols, so you do have to switch that part of your brain off. But as an actor, of necessity, you get over that very quickly. You're not starstruck on set, you're trying to get into your role. The professional switch on your brain goes on. We had a working relationship: she's the director, I'm the actor, these are our jobs. And then I'd go home singing 'Holiday',' she concludes with a giggle.

But was the catering all macrobiotic? Would Madonna allow the crew to look her in the eye? 'Madonna is completely down-to-earth,' says Natalie. 'She's an absolute professional. I meet fascinating people I respect and idolise all the time. It's such a beautiful gift of this job. And in my experience, the bigger the name, the more gracious and the more generous they are.'

Natalie grew up in Reading with her builder stepfather, housewife mother, sister Samantha, now 21, and brother Mark, 19, but is reluctant to discuss them. 'I came from a family that has nothing to do with the industry,' she explains. 'It was a very standard upbringing.' An only child until she was seven, her favourite game was dressing up and performing; she was also a keen dancer. But to her teachers at Reading Blue Coat School, she was an academic high-flyer. 'I'd probably always been a bit too repressed and well-behaved in my schooldays. I was head girl, a straight-A student, all those things,' she says. And captain of the netball team? 'Vice-captain.' She also travelled across the globe with her school's public-speaking team. 'So even though I hadn't dared to admit out loud to family and friends that I wanted to be an actress, I always knew that I did,' she says.