Q: Your character in The Counsellor is tempted by greed to act against his better judgment. How much does the theme resonate?

A:In Western capitalism we have been sold the idea that happiness and success go hand in hand, so the objects you attain define you. It's like, if I have nice things, I'm going to be happier and people will respect me more and I will be more attractive. My character, The Counsellor, makes good money but is surrounded by people with vast amounts of money, so he starts to be seduced by that. He buys a ring for his fiancee [Penelope Cruz] that probably cost about $300,000, which he can’t afford. He’s living outside his means and that leads him into an area where he has to compromise himself.

Q: You worked with Ridley Scott on Prometheus. What was it like working together again?

A: It was great seeing lots of familiar faces. Ridley works with an excellent crew, a great bunch of people, and I just love him to bits. He's got a great way with actors. He is fun and inspiring. It's something about that generation, Terrence Malick is the same. They have great energy levels and an industrious nature. I'm always trying to keep up.

Q: It must have been interesting doing the sex scene with Penelope Cruz, whose husband Javier Bardem was also in the film...

A: Javier was in the next room with the headphones [laughs]. No, they're both professionals at the top of their game and they're really great people. Javier did joke around when we were doing rehearsals. He came back into the room and was like: 'I forgot something.' But those scenes are always awkward unless you're both really into each other. The thing is to always make sure your partner in the scene is comfortable and doesn't feel like you're taking advantage of the space and the situation.

Q: Cormac McCarthy, the novelist, wrote the screenplay for The Counsellor. Are you a fan?

A: I was aware of his books but I'd never read any. I started The Road and I got halfway through. The problem is that unless I get through a book in a couple of sittings, I am not very successful in finishing it, which is kind of embarrassing. And I'm a slow reader on top of that. But when I read the script for The Counsellor, I was intrigued immediately. I thought it was an original piece.

What was it like working on Steve McQueen's 12 Years A Slave, which is bound to be up for Oscars, yourself included?

A: The film is beautiful and it's a really important piece. I think Steve has made a masterwork and I'm proud and very privileged to be a part of it. Whatever else happens after that is a bonus. I try not to think about awards. My work is done. Everything else is gravy.

Q: What do you look for in a role?

A: I like to explore morality but not to preach it. I like to explore human frailty and flaws and play provocative characters, so the audience leaves the cinema and questions themselves, the characters, relationships, life.

Q: What does Ireland mean to you these days?

A: Home, family... although I've been in London for 17 years now. I left Ireland when I was 19. They're kind of balancing each other out in terms of the amount of time I've spent in both places. But it's always great to get back to see friends. I grew up in the countryside, I long for some countryside when I'm in a city for too long.

Q: Was acting a dream as a child?

A: No, I had no idea what I wanted to do. I went through the gauntlet of the usual things, pilot, stuntman – a private investigator was a big one for a while. I realised I wasn't an academic person, I was better suited to practical learning. I thought of law at one point but I'm a slow reader so I thought, forget about that. Then I thought about architecture but failed my technical drawing exam.

Q: Why did you start acting?

A: The dream was to be a musician in my teens, so I went at that quite hard. I wanted to play lead guitar in a heavy metal band and practised for two hours a day. Then my friend came round with his guitar and just blew me out of the room. I was like: 'OK, well, he's got what it takes. I don't.' Around that same time I did a couple of acting classes and liked it.

Q: You work so much. Does your personal life take a back seat?

A: It does. I took a year off after Prometheus and before 12 Years A Slave, and now I'm on a run again. I'll work until next October, then I'll take another break. I recharge the batteries and then I feel like I've got the energy and strength to do a lot of work. I do think that, in the arts, there is a time when you will be doing your best work and you lead up to that – and then there's a time when you will go downhill. I'm trying to be as industrious as possible now while I'm getting the opportunities to work. Maybe I'll do something else in five years' time. Maybe I'll work behind the camera or find another challenge in life.