WHEN Frank McGuinness was 16 years old a dismissive teacher changed his life. "I won't say it was the making of me, because that would be giving credit to a man who set out to destroy me, " he says, "but if I survived that bollocks I'll survive other bollocks."

He'd just got his Intermediate Certificate. The teacher wanted him to do science. "But we had a terrible science teacher and I knew I wouldn't get the honour I needed to get a scholarship to go to college, " he says. Nobody in his immediate background in Buncrana had ever gone to university.

All the women worked in the local shirt factory. "If your father had a job, you were middle class, " he recalls.

"So I said I wanted to do history because I thought I could do it well enough to get an honour. He looked at me and said, 'You'll never get to university.' I remember saying nothing but inside I said, well I'll do it and I'll do it without you. And I did it. And that's been my motto. I rarely give up. In fact, I never give up.

"You have to have that side to you. On many occasions perhaps I should have given up. But I didn't.

Absolute ruthlessness may not always be the best policy. However, it's the only one I know. I have to follow my heart, no matter what."

His determination won him a place at University College Dublin, then a job as a lecturer at the New University of Ulster in Coleraine where he met his lifelong partner Philip Tilling, 15 years his elder. Patrick Mason recognised his raw talent in The Factory Girls, a play he wrote for a workshop in Galway in 1980 about women shirt workers in Buncrana standing up to their employers. It was accepted by the Abbey Theatre, and directed by Mason, as were his next two plays, Baglady and Observe The Sons Of Ulster Marching On The Somme, which won him the London Evening Standard Award for Most Promising Playwright.

Mason also directed Innocence, which caused uproar at the Gate Theatre with its explicit re-imagining of a day in Caravaggio's life.

"Patrick is an incredible force, " says McGuinness. "We're still friends, which is not common in theatre. We have survived each other, although we're not easy men by any stretch of the imagination, and eminently capable of killing each other. I put great store on his love and friendship and I'm immensely proud of his achievements."

Earlier this year, London's Almeida Theatre premiered McGuinness's 13th play There Came a Gypsy Riding . . . to plaudits from Michael Billington and other leading critics . . . while a new production of his Brecht translation The Caucasian Chalk Circle is on at the National Theatre. On Tuesday he joined Dermot Bolger, Patrick McCabe, Joe O'Connor and Colum McCann as a member of the Hennessy Hall of Fame, an award marking the achievement of major writers whose first work was published in New Irish Writing.

"I was 20, " he says. "I'd started writing at UCD but couldn't get into the student magazines. Then New Irish Writing published a poem about the death of my grandfather. And that really was the beginning of it. I knew what I wanted to do, although something in me knew that poetry was not going to be the medium. I remember I was paid �3.50, which in 1974 bought two steak dinners and a glass of wine."

We're sitting at a wooden table in the blue-walled cottage on Booterstown Avenue, a 25-minute walk from UCD where he lectures in literature. All his writing is done on this table. The room opens out onto a patio and narrow garden of trees and bushes, an oasis of quiet. I drink coffee from a Nicholas Mosse mug with the face of a cat given to him by his niece Selina. "She loves cats, and so do I, " he says. "They're like small children. The grief when they die is appalling." I try an organic chocolate cookie. "I got them for Philip, but he's not here."

The couple celebrate their 30th anniversary next year. "It's been a flash, really, " he says. I remark that I've been 45 years with my wife and we're still discovering each other: maybe relationships need mystery to survive. "It's the same with me and Philip, " he laughs. "There has to be some unknown."

Although his 2002 play Gates of Gold deals with the love of two men who have been together a long time, it was inspired not by his life but by Michael MacLiammoir and Hilton Edwards. He invariably draws on life but only to reimagine it. "If the facts lie, they are my lies, " he says.

He gestures to an armchair piled with books on Guy Fawkes. "I did a play for the Royal Shakespeare Company called Speaking Like Magpies about the Gunpowder Plot, of which I knew nothing other than it didn't work, that Guy Fawkes was not the ringleader and I knew that James I was probably gay. That was the extent of my knowledge. So I read those books and then just threw them aside and wrote as if from scratch, as I always do. I have this anti-historical gene. I cannot see a fact without turning it on its head.

I loved Michael MacLiammoir and Hilton Edwards too much to do a documentary on them. I wanted to spin a strange haunted story, something exotic, dangerous and dark that they would have appreciated and staged."

He never met MacLiammoir, but saw him perform his one-man show in the art deco bar of Lough Swilly Hotel in Buncrana. "It was one of those great nights. People were mesmerised by him. He was so disciplined, so absolutely focused. An extraordinary quiet spread across the place when he talked about Wilde. I was 18 and I'll never forget it."

While there were no books in his home in Buncrana, he steeped himself in Greek mythology and Shakespeare and modern drama courtesy of the BBC. "It became my encyclopaedia. Those were the glory days of British television with a whole new generation of anti-imperialists ruling the roost.

They put enormous emphasis on broadening the horizons. I had this cosmopolitan education in the wilds of the Inishowen peninsula. We were lucky as well because we had Derry only 14 miles away, where we could go to the ABC and see films without the censors crapping on them. When I was 15 or 16 I saw Midnight Cowboy uncut . . . my god, the shock of that." He was traumatised by the move to student digs in Dublin, just up the road from where he now lives. "I'd never been out of my home alone. I was so homesick I refused to warm to the city; but of course, unknown to myself, it was really becoming my territory."

The first play he saw at the Abbey was Brian Friel's The Gentle Island in 1971. "It was ahead of its time in terms of sexual politics and sexuality, " he says. Several of the cast would later have roles in his emergence as a major playwright. Playing the little boy was David Herlihy, who subsequently portrayed Dido in Carthaginians, an elegy to the dead of Bloody Sunday. Maureen Toal would become his "glorious muse" in a tour de force Bagladymonologue.

Bosco Hogan created the role of the loyalist volunteer Pyper, whose comrades were annihilated in the trenches but return to haunt him in Observe The Sons of Ulster.

"I'd probably run a mile if I met them in the streets of Belfast but they wouldn't go away. They were eight young men full of energy and full of purpose there in the room in my head, coming out.

They were good company for a while. They were in New York a couple of years ago. I went to visit them on their travels. I can talk very rationally about it now but when it was happening I certainly wasn't thinking rationally about it. I just went for it.

"That's what we were encouraged to do in the early 1980s when Patrick Mason and Joe Dowling and Sean McCarthy were out to get fresh blood into the theatre, writers like Bernard Farrell, Graham Reid and Neil Donnelly. They moved hell and high water to make the Abbey what it should be, putting money into new productions and into young writers' pockets. Not much but it was great, believe me. When the Abbey neglects this, it is in decline."

McGuinness has never lost this sense of daring. He has been a wonderfully subversive influence in Irish theatre, confronting political and sexual taboos with a poetic intensity that has undermined deep-rooted prejudices, not just with his original plays but in translations of classics. He enters into a creative dialogue with Ibsen, Chekhov, Lorca and Brecht undaunted by the fact that he's never been to Norway, Russia, Germany or Spain, nor speaks a word of any of the languages. "They come to me, " he says. His is a theatre of imagined worlds, not literal reality. "I loathe being predictable to myself even when I'm clearly mining a territory I've looked at before. I want to do something different with it.

That's part of the joy of it. I've no notion where things are going, absolutely no notion."

There Came A Gypsy Riding, set in Connemara, is about suicide, a theme he will soon return to with a BBC screenplay A Short Stay in Switzerland. "I think one of the terrible consequences of suicide is that it confronts everyone else with the possibility that they might do the same, " he says.

"There was a terrible tragedy in my own family. My cousin took his life, unexpectedly. I didn't want to exploit that, so he's radically transformed into a much younger man, a teenager. But there's no doubt that that event is the core of the play. I didn't want to examine the boy's decision, I wanted to look at its effect on his family. I'm not going to say it's a happy ending. It's not, by any stretch of the imagination. But it's an ending where there's life afterwards. And that's as much as you can take from it."

McGuinness doesn't do sentimentality. "There's too much Donegal ice in me for that. We're a very hard people. I'd like to think I'm a very violent mix of the rough and the courteous. That's what I like about the landscape of Donegal, its spectacular harshness with occasional signs of pleasantness. Not too much pleasantness, but enough to make it endurable. That's what my work tries to do."

There are no plans for an Irish production of There Came a Gypsy Riding. "It's a long time since I've had anything new in Dublin. I've theatres I can go to in London. It means I'm not dependent on anyone here. I'm not dependent on their commissions or on their good will. I don't need to lick arse.

It's terribly dangerous to have a single outlet or a single working relationship. For everybody concerned, it can only end in tears. I wish the Abbey and the Gate all the best, but I think they would understand me when I say I have to go elsewhere at times to get the challenges and the shaking up that I need."