Gregory Burke says he was only ever an accidental playwright.

Sitting in a cafe bar just around the corner from the Scottish Parliament, the writer behind Gagarin Way (a theatrical debut back in 2001 that ended up in the West End), the writer who gave us Black Watch (the play that went around the world and proved the worth of the National Theatre of Scotland), is telling me that he now realises that everything he wrote as a play was really a film in his head.

Thing is, he adds, he never went to the theatre when he was younger. "I barely went to theatre even when I was working in theatre. It's not a thing I love. I like it, don't get me wrong." But no, he says, everything he ever wrote was, in his head, really a movie.

That's what he does now. He writes screenplays. You won't have seen any of them. Not yet. Some of them you will never see. But next week one does make its way to the cinema: '71, a chase movie set in Belfast near the start of the Troubles, is Burke's first film credit. It's unlikely to be his last. Movies, he feels, are where he belongs.

"My type of writing is naturalistic. I don't think it's theatrical and, whatever happened with the plays I wrote, I don't feel..." He pauses, tries again. "Not that I didn't feel comfortable, but I didn't think it was me. I didn't feel I was writing about the things I wanted to write."

Given the power and success of his theatrical back catalogue, this may come as something of a surprise to you. But he is adamant. Plus, if he's honest, he likes working in cinema more. He prefers being one of the team. He prefers that it's not a writer's medium. "It's the director's film, which is a big difference from playwriting."

The playwright is the driver. The screenwriter is sitting in the back of the car. "Yeah, but I like that. That's one of the things I feel more suited to. Maybe I'm more comfortable with less responsibility. I like being able to write something and give it to the director and it's their choice what they do with it. I don't find that a problem at all. I'd say that's a relief to me."

If '71 - which also marks the film debut of director Yann Demange - is anything to go by, he will be enjoying less responsibility for some time to come. So far the reaction to the film has been good. It was widely praised when it was shown at Berlin earlier this year and it has just won the best film award at the Athens Film Festival.

It's an action movie really. A British soldier - played with close-mouthed intensity by Jack O'Connell - goes on his first patrol in west Belfast. He gets separated from his unit and has to try to make his way back to barracks in an unfamiliar city while being hunted by members of the IRA. The idea - based on real-life incidents - came from producer Angus Lamont. "We were just talking about it," Burke recalls, "and I'd just seen Apocalypto, the Mel Gibson film, and I said 'There's a pitch for you. It's Apocalypto set in Belfast', because it's just about a guy running and having to get home."

Didn't he worry that after Black Watch it was yet another military project?

"It's all I get offered, do you know what I mean? I wouldn't be doing any work if I didn't do that. It's just the nature of the business, isn't it? And particularly in films. Films get made because they're like other things. For all we might have a romantic view of the business, it takes quite a rare script to come from totally nowhere to get made.

''Even on '71 the budget was $10m and for Yann, for a first film, that's kind of unheard of. That's a lot of money for people to risk on something that is not like something else. If you have a problem with that you're probably in the wrong game. Like an actor gets typecast a writer has their bit of real estate and you get plonked there."

Still, he can offer you a different take on the story if you require it. From one angle he saw '71 as a take on Homer's Odyssey.

"The streets were the sea in this film and each house was an island, and you never know if on each island someone's going to help him or try to keep him there. At the time in Belfast there were a lot of factions going on. The Official IRA were Marxist-Leninists and different from the Provos who were coming up, and there was a generational struggle between them going on. There were the loyalist paramilitaries forming and colluding with the army. We had the MRF [the Military Reaction Force, a covert intelligence unit] who were almost a gang of their own in Belfast in the 1970s."

It's that messy uncertainty that the film captures well. "In that early part of the 1970s people were still quite mixed together and it was all very chaotic. As several of the old IRA guys and loyalists we spoke to said, the army didn't really know what they were doing when they first came. They were making it up as they went along, as were the guys who became the paramilitaries."

It is not, it should be said, a film about the politics of place. It is, as Burke says, an action movie.

"It goes back to Black Watch when you spoke to the soldiers and asked 'What about the politics of the Iraq War?' and they'd say 'Well, it doesn't really matter. It's got nothing to do with us at the end of the day. We're just trying to stay alive and if anyone points a gun at you, you shoot them. You don't ask what side they're on. That's all you can do. You can only try to stay alive.'"

How does he now look back on Black Watch, the play and the phenomenon it became?

"It changed everything for everybody. It gives you a higher profile in an industry sense. I don't know. It's quite odd. John [Black Watch director John Tiffany] went into that super league of directors. But for me ... I don't know ..." He is fumbling again, uncomfortable talking about what was before recognising the mark it has left. "I'll probably always be known as Gregory 'Black Watch' Burke. That's the legacy of it."

That was then. The future for Burke is sitting in his home in Dunfermline writing scripts for films and TV. He's written more screenplays than plays, "which again shows you where I should have been working because it took me 10 years to write five plays. I've got quite a few projects on the go. I've got more work than I can do. If I could clone myself I'd be in a fantastic position."

Is it a help or a hindrance being based in Fife? "You could say it's an advantage or a disadvantage. For writers, the less distractions the better. But at the same time there's also an argument that the more you're in a network, the more work you get." But then networking is not really him, as he claims he has never socialised with people he works with. Anyway, he says, right now he's too busy working to do much else. "You get to a point in your life when you say 'Okay, I'm going to work really hard now. I'm going to concentrate on this."

He agrees that '71 is a vindication of this policy. "I think the more you write the better you get at it. But then tomorrow everybody could decide someone else can do soldiers and then that's you back to dishwashing."

'71 is released in cinemas on Friday