Masters of Sex: Michael Sheen tells of taking sex scenes to a high end, unusual level Masters of Sex stars Michael Sheen and Lizzy Caplan, who will portray the real-life pioneers of the science of human sexuality, William Masters and Virginia Johnson. Michael Sheen as Dr. William Masters and Lizzy Caplan as Virginia Johnson in Masters of Sex. MICHAEL Sheen - star of the Twilight franchise , Tron: Legacy and Frost/Nixon - has had more than a few unusual on-screen couplings. There was the time he had sex with a vampire while hanging backwards over a cliff in Underworld: Rise of the Lycans. Or when filmmakers covered him in chocolate powder and made him bark while doing the deed in Dirty Filthy Love. The closest he ever came to a conventional sex scene was with Stephen Fry in Wilde. "They've all been fairly unusual," he says in a gently lilting Welsh accent. I was trying to think about one conventional or normal sex scene that I've done and I couldn't quite think of one to be honest. Lizzy Caplan as Virginia Johnson in Masters of Sex. There's plenty more unusual sex on display in the Showtime series Masters of Sex, which screens here on SBS. The raunchy high end drama tells the real life story of pioneering sexologists William Masters and Virginia Johnson (Lizzy Caplan) whose groundbreaking research from the mid '50s onwards, attaching electrodes to couples making love in the lab, helped debunked many of the myths and assumptions about sex held by the medical and psychological establishment at the time. "It's the sheer volume of (sex) in this that was different and also the way it's done," he says. Being wired up and doing quite physical movements was always a bit of a challenge, but it's something that certainly me and Lizzy got used to quickly because we were involved in it quite a lot. But I don't think the (guest) actors coming in and doing scenes ever got used to it. Michael Sheen as Dr. William Masters and Lizzy Caplan in Masters of Sex. Putting sex to one side, the core of this series is the relationship between the cold and clinical man of science Masters and the twice-divorced former nightclub singer Johnson. He hired her more for her matter-of-fact views on sex and ability to persuade subjects to join in the research, than her non-existent academic background. The real Masters wound up leaving his wife Libby (played by Caitlin FitzGerald) for her, after the sexologists began engaging in some "research" of their own. "The dynamic is he's in equal parts attracted and repelled by Virginia and that always makes for an interesting relationship so I have a feeling people will want to tune in again, week after week," Sheen says. Considering the series could have lived or died on the chemistry between the two leads, surprisingly little work went into ensuring the actors - who'd never met - were actually compatible. "It wasn't like we went through a whole series of auditions together to work out whether it would work or not, so it was a bit of a gamble," he says. But it seemed to work out pretty well. Michael Sheen as Dr. William Masters in Masters of Sex. In real life, Sheen is almost as famous for his string of high-profile relationships as his acting career. He has a daughter, Lily Mo Sheen, from his eight-year relationship with Kate Beckinsale and he's dated English ballet dancer Lorraine Stewart, and actor Rachel McAdams, who he met filming Midnight in Paris. They broke up earlier this year. Recently Sheen has been seen squiring on-screen wife Caitlin FitzGerald. Sheen doesn't appreciate the attention. "It's my private life and it stays private," he says, firmly. I can see that it's a culture that's very interested in that stuff, but I've got no interest in talking about it. Sheen has specialised in playing real-life characters, including former British Prime Minister Tony Blair in Peter Morgan's trilogy: The Deal, The Queen and The Special Relationship; he took on outspoken football manager Brian Clough for The Damned United and TV host David Frost in Frost/Nixon. Nicholas D\'Agosto as Dr. Ethan Haas, Michael Sheen as Dr. William Masters, Lizzy Caplan as Virginia Johnson, Teddy Sears as Dr. Austin Langham and Caitlin Fitzgerald as Libby Masters in Masters of Sex. He admits it's not always easy to let go of mannerisms, accents and personalities after filming is through. "It's not something you can just take off like a suit of clothes," he says, adding it takes a period of "decompression" after each role, and even then, he's changed by the experience. "There is a little part of each of the characters that stays with you," he says. Sheen was extremely sad to learn of Frost's sudden death of a heart attack six weeks ago. After reading and watching so much about the broadcaster to play the role: "inevitably a kind of intimacy grows up - a very one-sided intimacy. I felt like I knew him very well and I did in one way, but I only knew him a little in actuality in terms of the time we spent together. I was very fond of him and so very sad when he died.