At one point, Don Cheadle's fish-out-of-water FBI agent wonders if Boyle is really dumb or really smart (though the language he uses is considerably more colourful). What's your view?
I think it's pretty obvious. The last really dumb person I've found reading Russian novels was a long way back. Boyle deliberately gives the impression of being dumb so that people underestimate him and leave him alone.
A New Yorker critic charged Martin McDonagh with racism in his latest play, A Behanding in Spokane. There are a lot of racist lines in The Guard, too - most of them spoken by your character. Did any of it make you uneasy?
I thought that New Yorker accusation was very unfair and off the mark. I can kind of understand the argument and I think it had more to do with the production than the actual writing, but I know it's not true. With The Guard, if I thought Gerry Boyle was fundamentally racist I wouldn't do it, unless it was going to explore what was wrong with it. But with Boyle it's a ploy: he throws as many bombs as he can, hoping to flush people out and see their true colours.
You recently got a green light to direct your first film, an adaptation of Flann O'Brien's 1939 novel At Swim-Two-Birds. How long has that been in the works?
Seven years. The rights came up in 2004 and I just grabbed them, not knowing what I was going to do with them. It's one of my favourite books. I read it at 17 or 18, and to have a book that reflects all the maelstrom and confusion of being a teenager was such a glory back then - and it still feels relevant now. We're set to shoot in the spring, but I'm not counting my chickens yet.
How do you film a supposedly unfilmable book?
A friend of mine said: "Yeah, but the book was unwriteable," so that sorts that one out. It's going to be kind of Wizard of Oz-ish, in the sense that the people who populate the real world also populate the [main character's] imaginary world. Almost every actor will have two personas. I think film is uniquely suited to this, because you can change worlds in a second. The trick will be maintaining the madness and anarchy of the book while making sure a cinema audience can still follow it.
Of all the directors you've worked with, who has impressed you the most?
I worked with Steven Spielberg on AI and his level of preparation was extraordinary. He told me there was a time at the beginning when he was a bit more spontaneous and went over budget and it absolutely wrecked his head. When you look at the power and assuredness of his movies, it makes sense that he works out so much in advance. It's never going to be that way for me though. I wouldn't even try to aspire to that: it's just a different way of working.
Has appearing in three Harry Potter films impacted on your private life?
Not overly, because as unconventional as my looks are, they're not quite as unconventional as Mad-Eye Moody's, so I've kind of got away with murder. Robbie Coltrane told me I should forget about walking through airports again but, to be honest, it's a bad idea to tell your 10-year-old to talk to me, because the poor child makes no connection with Mad-Eye Moody and he's looking at me saying, "why am I being asked to talk to a stranger?"
You have four sons of your own. Were they excited when you got the part?
They were the reason I did it. They all roared when they heard. "Dad's going to be Mad-Eye Moody. Wa-hey!" After that, it was never not going to happen.
Two of your sons, Brian and Domhnall, have become actors. What advice do you give them?
Make your own work. Hire a room, round up 30 people, at lunchtime or whatever, and put on a play. Being at other people's behest is the worst part of this job, so my advice would be to actually practise your craft. Just do it.
What's next?
John Martin McDonagh has written a script called Calvary about a good priest in an atmosphere where the priesthood is reviled. We cooked it up one night, just talking. It must be really difficult now to be a good priest, given how you've been let down by everything around you. I am interested in good people as well as bad. Not purely good - that would be really dull - but I like the notion of mixing great and terrible figures with ordinary men.
- TimeOut / Observer
