John Simm's first costume drama casts him not as a pretty boy saviour but as a scarred antihero. The Devil's Whore is such an ambitious project about the English Civil War that Peter Flannery, who wrote Our Friends in the North, spent a decade working on it. The illustrious cast includes Michael Fassbender and Dominic West, and there's a terrifically camp performance from Peter Capaldi.

"Yeah, because I look a right mess. Dodgy haircut, beard, a metal hand, a scar down one side of my face. The make-up burnt right through to my flesh; it was agony. But with every part there must be some suffering, or it's too easy being an actor." And the pompous expression turns into a huge grin.

The Devil's Whore reunited Simm with his old friend West; the pair had worked on Diana & Me in 1997, a film so dire that it was later shelved. "We filmed in Sydney for a few months and had an amazing time; Dominic and I were like Batman and Robin. As is normal in this industry, I didn't see him again for years. I bumped into him in LA and he'd been filming The Wire in Baltimore. He told me it was a nightmare, that no one would ever watch it."

Simm forgot about this conversation until, years later, The Wire became widely regarded as one of the best television programmes yet made. He took the box set with him to South Africa, where The Devil's Whore was filmed. "I'd be working with Dominic all day and watching him on DVD all night. I kept asking about The Wire until I realised I had to stop." To pass the time, he borrowed Michael Fassbender's guitar (Simm grew up playing in a band with his father and, until recently, had his own band, Magic Alex). "Michael was out on benders and I'd stay in, strumming away. That's how old I am. It's over."

I remind him that as a teenager he wanted to be Tom Cruise by the time he was 27. "It was never going to happen. Obviously. I'm no longer that ambitious." He pauses and stifles a laugh at the cliche to follow. "And I don't care, because I'm really happy."