Sophia Myles tells Eddie Harrison about being the new ‘it’ girl of British cinema.

As a teenager, Sophia Myles faced a straight choice: study philosophy at Cambridge, or pursue her acting career. Myles chose the latter and, while her plum role of Lady Penelope in the £60 million Thunderbirds movie may not have translated to box-office results, the international exposure launched the London-born actress towards the top rank of Hollywood stars.

Since then, the 26-year-old has been in constant demand; playing opposite Kate Beckinsale in the two Underworld movies, joining an all-star cast for Terry Zwigoff and Daniel Clowes’s follow-up to Ghost World, Art School Confidential, and with David Tennant in a forthcoming episode of Doctor Who. Myles’ latest cinematic role is in Tristan & Isolde, director Kevin Reynolds’ 13th-century romance. The part of Isolde, a youthful future queen whose public scrutinise her every move, is one she felt considerable empathy with. “I’ve always done exactly what I want to do, and Isolde is similarly headstrong about wanting to live life exactly as she wants, no matter what people think,” says Myles. “When we were rehearsing, Kevin Reynolds asked James [Franco, who plays Tristan] and I if we’d ever been in love with someone, because he knew that the role demands that kind of feeling. I certainly know what it’s like when you meet someone and they just turn your world upside down.”

In Reynolds’ movie, Isolde’s love for Tristan is thwarted by her marriage to Lord Marke (Rufus Sewell). The romance is distorted by the strict rules of honour and duty in medieval society, something Myles feels has plenty of contemporary relevance. “When I first heard the names Tristan and Isolde, the first thing I thought of was Wagner, but I didn’t know it’s a story that’s been passed on orally from as early as they 13th Century,” she says. “I think the reason it’s endured is because it contains universal themes of love and infidelity. Back then, they had such strong feelings of duty to their country, and although their love starts of pure, they have to hide their relationship, which turns it into something seedy and unhappy. The problem is that Tristan thinks with his head, but Isolde with her heart, and I think men and women are still like that.”

The role confirms Myles’ rapid ascent to stardom, and she admits the constant media attention sometimes makes it hard to keep her feet on the ground. “I can’t believe what’s happened to me in the past ten years; this all started when I was 16 and I was spotted in a school play. Suddenly, I was doing press junkets in Japan for Thunderbirds, and It can feel a bit overwhelming, so I always invite a friend to come along with me. I need someone to keep me grounded in the real world.”

Myles’s upcoming television role, however, is in a very unreal world. She appears in The Girl in the Fireplace, the fourth episode of the new series of Doctor Who. “I play Madame De Pompadour, the mistress of Louis XV at Versailles, and also I’ve got a but of a history with the Doctor,” she says. “And there’s a threat, of course, in the form of some clockwork mechanicals.”

In the meantime, Myles is working in Edinburgh, shooting David Mackenzie’s fourth feature, Hallam Foe, with Jamie Bell. But while the work keeps coming in, she’s philosophical about her status as the new ‘it’ girl of British cinema. “The most exciting thing for me is that I genuinely love all the roles I’ve had,” she says. “Playing Lady P, in particular, gave me so much confidence, and I still miss driving the FAB 1 car. All I can hope for in the future is to keep getting roles as good as the ones I’ve had.”