Hugh Dancy: 'I was told I'd always be cast in posh parts'

When Hugh Dancy took his first steps in acting more than a decade ago along the usual British TV paths (Kavanagh QC, BBC adaptations of classic novels), he worried about being typecast. "The doubting part of me assumed that I would spend my career playing posh characters in costume dramas," the 36-year-old says when we meet at his publicists' office in Soho. "At least one casting director told me bluntly that that's what I'd be doing, so get used to it."

He's done the occasional costume drama since, but Dancy's background, growing up in an academic household in the Midlands and studying English at Oxford, didn't stop him from playing a New Yorker with Asperger's syndrome in the acclaimed 2009 indie drama Adam – and that casting director probably didn't foresee the "gay, Buddhist, wine-bar owning, marathon-running cancer patient" he played in the US TV hit The Big C. "I described the role to a friend of mine, slightly despairingly, before I started filming, and she said, 'Well, at least somebody out there has a healthy respect for your range.'"

On the surface at least, his latest part doesn't seem that big a stretch. In Martha Marcy May Marlene, one of the big break-out successes of last year's Sundance festival, Dancy plays a well-heeled Brit (Ted) living in New York with his pretty American wife. Their peace is broken when his wife's troubled younger sister, played by Elizabeth Olsen, seeks refuge from a sinister cult at their hideaway.

Dancy, who lives in New York and is married to the actress Claire Danes, acknowledges that "this couple, me and my wife in the movie, are perhaps the most normal, recognisable people in it", but warns against trying to pin down anyone in the film. "The characters have all got mixed motives. At moments, Ted is very likable but, potentially, there's a bullying, violent thing in him too."

Dancy, by contrast, comes across as impeccably nice and understated in a way that New Yorkers must find so English. He met his wife on the set of the 2007 film Evening and they married two years later. I ask him if he had eyes for her before their first meeting. "I saw her in Romeo + Juliet when I was in university and all I remember really thinking was that she was far and away one of the more successful actors in that movie when it came to speaking the verse."

Given his impressive capacity for restraint, I'd love to see Dancy in Venus in Fur, the new David Ives play he's currently starring in on Broadway. He plays a reserved theatre director drawn into erotic power games by a brazen actress he's auditioning. No wonder the reviewers thought it made for great theatre: watching Dancy losing his cool in dramatic fashion must be something to behold.

Martha Marcy May Marlene is in cinemas now