Writer Owen McCafferty and actor Patrick O'Kane thought they knew their latest play, but its darker side emerged during rehearsals, they tell Jane Coyle

There are a number of life experiences which bind writer Owen McCafferty and actor Patrick O'Kane - growing up in the same area of south Belfast, parallel success stories in the theatre and, not least, their passionate devotion to Manchester United.

Since 1999, when O'Kane joined James Ellis and Stella McCusker at the National Theatre in London for a reading of McCafferty's play Tonto's Way, their names have regularly appeared side by side on cast lists and programme notes. O'Kane played Socrates in the Manchester Royal Exchange production of Shoot the Crow, and last year was one of the highly praised group of Northern actors in Scenes from the Big Picture at the National, for which McCafferty clocked up an unprecedented trio of prestigious UK theatre awards.

Last year, their association moved a step closer, when McCafferty made a fine directing debut for Prime Cut with Harold Pinter's chilling double-hander Ashes to Ashes, in which O'Kane and Michelle Fairleigh made the blood run cold in the veins of the audience at the Lyric Theatre.

Now they are together again and in even closer proximity - just the two of them, closeted away in an upstairs room of the Old Museum Arts Centre, rehearsing, reshaping, deconstructing and reconstructing McCafferty's Cold Comfort, the piece which O'Kane believes to be his darkest yet.

On the surface, it is the story of Kevin Toner, a man who returns to Belfast from London to face his demons and have a final conversation with his father. But ask them about the underbelly of the play and they go all silent and thoughtful. Eventually, McCafferty offers an opinion.

"This play . . . the more we do it and the more we talk about it, it feels that it is about a lack of communication. Its focus is a conversation between a son and a father."

"But", adds O'Kane, "the father can't take part, because he's dead. The son has come home in search of resolution and absolution, but he receives neither. It's both a voyage around my father and a contemplation of parenthood."

The play was commissioned five years ago by Paines Plough, as part of an award won by McCafferty for Mojo Mickybo - recently adapted as the feature film Mickybo and Me by writer/director Terry Loane. But the company decided it was not for them and did not produce it. Since then, it has gone through a number of possible permutations.

It was workshopped at the National with O'Kane directing Conleth Hill in the central role. Then director David Gothard stepped in, with O'Kane playing Toner. There was even a fleeting suggestion that McCafferty himself might act in it.

Both acknowledge, however, that it was Gothard who uncovered new depths and layers, which might never otherwise have occurred to them.

"David introduced the idea that it was bigger than we thought," says McCafferty. "He drew our attention to comparisons with Hamlet, a man obsessed and unreconciled with his father, haunted by the past - a role which Paddy is actually due to play later in the year."

"I also read Beckett's Molloy and found it helpful," says O'Kane. "The thing was, we thought we knew the piece so well, but during rehearsals these past couple of weeks, it has taken on a new life of its own. It was a bit weird, but we had the same idea at the same time and have taken it out of the realms of the kind of theatre that pretends to be real and made it more about the imagination. Like all Owen's plays, it's very funny but also deeply disturbing. Something really bad happens, but you don't see it coming.

"The great thing about Owen is that he loves actors and actors respond well because he writes so well for us. He's very good at dialogue and his plays are a joy to work on."

While O'Kane has lived permanently in London since graduating from the Central School of Speech and Drama some 15 years ago, McCafferty remains based in Belfast. But sightings of him are becoming increasingly rare and largely dependent on where in the world there happens to be a production of one of his plays. He is a bit of a darling on the London scene these days - much in favour at the National Theatre, where he was writer in residence in 1999, and recently invited by Sam Mendes's company, Scamp, to write a play of his own choosing.

The result was the critically acclaimed stage adaptation of Days of Wine and Roses, premiered a couple of months back at the Donmar Warehouse in London's Covent Garden.

O'Kane went to see it and declared it a story that McCafferty had very much made his own.

"I had done a version of Ionesco's The Chairs a couple of years back for Tinderbox," McCafferty says, "so the notion of doing an adaptation was not a new process. But there was no point in trying to recreate the movie - if that's what you want, get out the video. I was keen to give it my take, my view. I was really pleased with the support and the response it received."

But in spite of his hard-wrought success and current bankability, he has lost none of his black Belfast humour and sense of proportion.

"These things tend to be cyclical," he declares. "You can be flavour of the month for a while and get carried along on the momentum of your own success. Don't get me wrong, I'm not decrying it, but it is a case of making hay while the sun shines.

"I've been writing for 12 years, so I'm not exactly an overnight success. But I did make a conscious effort to get my work on in London, partly for economic reasons. It was never a case that I felt people here don't understand me and I must move on. If I did feel like that, I wouldn't be back. It was about giving myself a challenge, too. It's fine for people at home to say you're good, but you need to open up the gate and test yourself in the wider world.

"My biggest kick so far was seeing Scenes from the Big Picture in Macedonia and hearing the audience laugh and stay quiet in all the right places. It was previously done in LA, where it went down OK, but audiences didn't get it in the same way. The word 'Belfast' is only mentioned once, but someone in Macedonia told me that I could just has well have been talking about Skopje."

O'Kane expresses no great surprise to that reaction, pinpointing McCafferty's uncanny ability to set a play in Belfast without it being parochial.

"It starts here, then reaches all humanity. It's an irony that in touching the specific, you move into the panoramic."

Both are now looking toward new horizons. O'Kane has just been awarded a coveted NESTA (National Endowment for Science, Technology and the Arts) Fellowship, one of the first actors to have received one. "They identify individuals who are considered to have achieved a level of excellence in their chosen fields. Another Belfast actor, Carol Moore, has also received one. My project will look at the actor's part in the creative process and will be funded for a three-year part-time period. It's something completely different for me, but definitely a new challenge. Then later in the year, I get to fulfil what I guess is every actor's dream, when I play Hamlet in Dublin and Belfast, in a co-production between the Lyric and the Abbey."

Meanwhile, McCafferty has a play to write for the National - "I owe them one" - and is also writing a musical, though he can't say any more about it at present - "probably because he hasn't a clue what he's doing," jibes O'Kane.

They reckon their working relationship works well because they have a similar sense of humour and common sense, and are both honest and rational about what they do.

"There is never any pulling out of hair or mad rages," says McCafferty. "It's only a play, after all - not rocket science. And I don't know if it comes through in the work, but we share a socialist view of the world and that's an important part of our artistic partnership."

"We're not very disciplined, though," admits O'Kane. "We tend to go into a room and do a vigorous workout by putting on the kettle and standing around it. Then we kind of hang around and see what happens next."

What actually happens next is that an executive decision is taken to go out for a cup of tea and the pair of them wander off across College Square in a leisurely fashion, chatting about the FA Cup Final, totally immersed in their own version of the creative process.

• Cold Comfort, by Owen McCafferty, will be premiered by Prime Cut from May 5 to 14 at the Old Museum Arts Centre during Belfast's Cathedral Quarter Arts Festival. It then tours to Galway (May 17), Cookstown (May 18), Armagh (May 19) and Derry (May 20 and 21)