Aidan Gillen made his name playing chancers and scumbags and in his new BBC drama Freefall he portrays a venal City banker

It’s not easy to interview someone who you’ve last seen masturbating. But so it is with Aidan Gillen. As I approach him in the National Film Theatre foyer, I can’t help recalling a scene I’ve just watched. He plays venal City banker Gus in the forthcoming BBC credit-crunch drama Freefall; after clinching some ghastly multi-billion sub-prime deal that ultimately leads to the debt-ridden immiseration of thousands, Gus retreats to the office loos to celebrate in the manner he deems most proper. Never has the cockney rhyming slang “merchant banker” been quite so luridly literalised.

Harold Pinter described Gillen as “dangerous” after seeing him appear in a 2003 Broadway production of The Caretaker. As I walk towards him he wraps and unwraps his legs around each other repeatedly. His whole demeanour is an heroically uncomfortable array of twitches and leers.

“Having talked to a lot of those guys in banking, I realised that high finance is very exciting,” he says as we settle down in the bar. “It probably is terribly exciting to watch these deals fall into place.” But surely not so terribly exciting as your character finds it? “I don’t know. I don’t want to get too wanky about it, but I can totally sympathise with him. There’s pleasure in his life but there’s nobody to share it with. Hence, you know, that scene.”

Gillen is no stranger to, you know, challenging scenes. A decade ago in Queer As Folk, he played Stuart, uttering the infamous lines: “I’m a faggot-ass, fudge-packing, shit-stabbing uphill gardener. I dine at the downstairs restaurant, I dance at the other end of the ballroom. I’m Moses and the parting of the red cheeks . . . And I am not a pervert.” (Gillen, a former Dublin altar boy, recalls watching some sex scenes from Queer As Folk with his mother. “She said: ‘How are they actually doing that?’ And my brother-in-law said: ‘It’s trick photography.’”) His performance was, like the series, widely praised. It was also typical of his astute preference for edgy small-screen dramas in recent years.

Before Queer As Folk came the role of Gypo in Antonia Bird’s Safe. At one point Gypo, a young homeless man, plunges a bottle into his chest in order to get free hospital treatment. More recently, Gillen starred as Baltimore mayor Tommy Carcetti in The Wire, a political reptile who unexpectedly grows a spine and a conscience while in office.

How did Gillen get the role? “They were casting the net wide getting actors who aren’t recognised, so that’s how us lot [he means the British and the Irish – Dominic West and Idris Elba also starred] got into it. It worked. I’d just been in The Caretaker on Broadway, which meant nothing perhaps to TV audiences there, but showed I could do what they wanted. Also many American actors don’t really want to blot their resumés by appearing as scumbags. British actors – and Irish ones too if I’m anything to go by – are less bothered about playing disgusting or even flawed people. They’re often the most interesting roles, after all, but in the US they can be career death.”

Gillen’s resumé, then, might not make much sense to an American actor: it teems with reptiles, chancers and scumbags (he was particularly effective as Mick, the swaggering, volatile pipe dreamer in The Caretaker, and as the slimy real-estate agent Richard Roma in a West End production of David Mamet’s Glengarry Glen Ross). But he is proud of it. “There’s a common thread through Antonia Bird, Queer As Folk and The Wire,” he says. “I have been in control of what I’ve been doing, of the career I’ve put together.” I’m not sure how that control includes, say, his turn in the Jackie Chan-Owen Wilson buddy-chop-socky sequel Shanghai Knights, but let’s not spoil the story.

“I’ve made a point of trying not to play the same part, and of moving between theatre and film and TV. The idea is that by the time you come back you have been away for a year and people have forgotten you. If you like having time off, which I do, that’s a good career strategy. Or at least, it’s my strategy to keep my head together. I keep going back to Ireland to reboot. And then return, showing up as someone else.”

Freefall marks Gillen’s return to British TV drama after too long away. “When I was 19 growing up in Dublin, I wanted to come to London. I’d done a lot of Irish stage work, which was great [in Billy Roche's A Handful of Stars, for instance], but London was a magnet . . . the place where the great TV dramas were made. It was like someone wanting to be in a rock’n'roll band now.”

His fellow Wire star Dominic West has said that the UK lacks quality contemporary drama on TV. He told Radio 4′s Today programme recently: “If you turn on American TV, there’s a huge choice of nothing you want to see and, unfortunately, I think that’s the case here now as well . . . we don’t seem to be able to do contemporary stuff.” Does Gillan agree?

“So-called reality TV, which dominates British channels, is destroying what made it cherishable to me and lots of others in the first place. I loved Alan Clarke, Ken Loach and Alan Bleasdale’s work. In fact the first TV dramas I ever saw were Screen Twos produced by David Thompson, who also produced a lot of Alan Clarke. And now David produces Freefall, so it shows the kind of British TV drama I admired is not quite dead.”

That said, Gillen has now retreated to live in Ireland and works there as much as he can. “I just wanted to get back home. I have always been travelling – New York and London. I want to give my kids a proper home.” He lives with his wife Olivia O’Flanagan in Kerry, and his children Berry and Joe attend a Gaelic-speaking school. “They have been brought up in London but because they have Irish parents they seemed to have an Irish accent – then when they got out to Ireland they sounded like Oliver Twist.”

His latest project is to star in the first Hammer film of the 21st century. Called The Wake Wood, it doesn’t sound like the camp Hammer horror that made films starring Ingrid Pitt and Peter Cushing so diverting 40 years ago. “No, it’s nothing like that. It’s an Irish film written by a guy I know [writer-director David Keating]. It’s the kind of horror film that I like – The Exorcist and The Wicker Man.”

The film tells the story of a couple, Patrick (Gillen) and Louise Daley (Eva Birthistle), whose nine-year-old daughter is killed in a dog attack. To escape their grief, they relocate to a remote rural community. The locals introduce the couple to a secret, pagan ritual that will allow them three more days with Alice before she is returned to the ground for ever. But what will they do when it’s time for Alice to go back? Gillen sensibly won’t divulge.

Why did he take the role? “I like to mix it up and do something completely different.” It was, he says, “literally the smell of the paint” that made him become an actor in the first place: “I was building and painting the sets. I didn’t want to go to college or work in an office or have a nine-to-five job. I knew that quite clearly before I left school.” He is 41 now, and in the intervening years says he “definitely thought about stopping more than twice. I have been doing this since I was very young. If I could wind it back I would have another life – I would like that, but I would also like to have this life too. For me, now, working and children is it. There’s nothing more to life” •

Freefall is on BBC2 tonight at 9pm. The Wake Wood will be released later this year.