ON the day that a Lurgan car bomb ripped Rosemary Nelson to pieces, Gary Mitchell was absorbed in the final rehearsal for the play he hopes might expand our perception of loyalists and their raw, unyielding creed. That night Trust previewed at the Royal Court Upstairs in London, its gripping insight into lives of hard, ugly vigour terribly intensified by that day's appalling events. Hours earlier the Red Hand Defenders had claimed ''responsibility'' for the murder of the Catholic human rights lawyer, as if atrocity had now made them ''responsible'' individuals. But, as Mitchell knows, words, too, get hijacked by either side in Northern Ireland, loyalists or republicans contorting them to suit their own particular poisons. So trust there becomes not an act of faith but a pledge of mindless allegiance born of terror. Within a community, Mitchell shows it to be the code word for vigilante muscle.

Within the home he lets it hang in the air like a curse, the very opposite of itself, maiming everything and achieving nothing but betrayal.

In the past five years some of the best new theatre in Britain has come from across the water. But while Conor McPherson, Martin McDonagh, Sebastian Barry, and Mark O'Rowe spring from a Catholic background, Mitchell is that rare creature, a playwright from a Protestant working-class redoubt. Now, with this latest work, he has strengthened that distinction and his sheer courage in following that lonely career path can't be underestimated: Mitchell still lives in Rathcoole, the vast, brutalised scheme in north Belfast which, in the fifties, was ''mixed'' in every sense.

''Rich and poor, Protestant and Catholic, we had them all in a population of around 20,000,'' he says. ''Now there are no rich people, and hardly any Catholics, and that's all because of The Troubles. Nothing else.'' Mitchell sets Trust in a lingering UDA stronghold of Rathcoole, where internal feuding is the only reason to converse. He doesn't seek to justify his community's virulent commitment to intransigence but to examine how, even inside its own home, that reflex contaminates, punishes, and ultimately destroys those it most wants to protect. Yet if Mitchell is taking his own people to task, he is also challenging the No Surrender mentality of every power bloc in Northern Ireland. But, despite his best intentions, is he also reinforcing the stereotype rather than dissolving it.

On his way back to Rathcoole Mitchell - catching up with Trust's enthusiastic reviews - contemplates that dilemma solemnly. There is a steady-eyed directness about his face even in repose, but the tight, unadorned tempo of his speech still finds room for the ironic. ''I never said that I was here to re-write stereotypes,''

he replies. ''My problem is that the nationalist/republican Catholic cause has been overly romanticised, and every time you see a Protestant on stage, he's just the worst thing in the world, either very evil or very boring.'' There are elements of evil in everybody, says Mitchell. ''But there are also elements of good, and in writing honestly I try to strike a balance.'' We talk about the valour of David Ervine, leader of the Progressive Unionists - founded as the political wing of the loyalist paramilitary UVF - who last year, at a public meeting in Belfast, urged Protestants to confront the fact that they hadn't made the most of their own culture.

Ervine was jeered for suggesting that loyalists should stop blaming nationalists for the wide appeal of Irish dancing, the Bodhran, and all the rest. ''What have we got,'' he challenged. ''The Orange marches, that's all.'' Mitchell reflects that Ervine was spot-on. ''The first thing we have to do as a community is hold up our hands and say: 'Okay, we're pretty much to blame because we haven't attempted to put our side across in any good or entertaining way.' I wouldn't be a great fan of Riverdance, or anything like that, but many people are, and the Irish do market their culture exceptionally well.''

Even in London, Mitchell observes that ''a great Irish spirit'' prevails, but his community, dedicated so ferociously to the British Crown, ''just doesn't seem to be here at all.''

This loyalist sense of dislocation, once outside the bunker, is among the most bleakly tragic aspects of Northern Ireland's long war. And one imagines that, given the warping force of grievance, no-one in Rathcoole will thank Mitchell for parading before the world its hard reliance on the rule of violence. Not so, he says, although he adds sardonically: ''Maybe writing plays is not something Rathcoole residents aspire to, but when my first play - In A Little World Of Our Own - was put on in Belfast, about 90 folk from the estate came. They'd never been in a theatre before and they thought the whole thing brilliant.'' Why, then, so few contemporary Protestant writers compared to the numbers from other side? ''It's like I said: there's no dignity perceived by my community in doing this. My people think the theatre is a small thing, and writing plays an insignificant pursuit. Not long ago, for

instance, I was coming out of a petrol station in Rathcoole, and a woman stopped me and said: 'Hello Gary. I hear you won a wee award for your wee play . . .' That sums up what my community think about it, and I like that kind of attitude.''

So Mitchell remains in Rathcoole, staying in the parental home he's always known, and the neighbourhood is, after all, the wellspring of his writing. Like most of his friends, he left school at 15 and then, after eight years on the dole, he joined the lowliest rung of the Civil Service. ''That was far more demeaning than no work at all, and I hated it . But it did inspire me to do something with my life that was legal and good.'' Did he withstand the pressures to enrol with paramilitaries? ''Yes, because I joined a local drama group, but what people forget is that when I was young the UDA and the UVF were legal. It was like joining the Scouts. There was a sort of pride about it. You were almost a policeman, almost a soldier supporting your community. Then everything deteriorated into an area of total unemployment and practically unemployable people.''

His creative escape route was through writing for radio. Unburdened by qualifications, Mitchell still managed to be a winner at various Young Playwright festivals, each of his pieces highlighting the people he feels are continually misrepresented and therefore misunderstood. Today, with commissions rolling in, he can live by writing alone, but is he in danger of becoming a one-theme dramatist? The question scarcely worries him. ''Actually I'm working on a play for the National here, called Marching On, and I suppose you can guess what that's about. My community, in fact, is multifaceted but that's rarely been put across. It's also very humorous, although in Trust we had to cut back on that because people were laughing too much, and the play was turning into a rip-roaring comedy.''

Certainly Mitchell himself is more amused than downcast by the fact that much of his reputation has been made in Dublin where the Abbey Theatre's production of In A Little World Of Our Own won Best New Play in the 1997 Irish Times Theatre Awards. And while no nationalists are portrayed in Trust, all the key characters are played by Catholics. Is that progress, or happenstance? Mitchell laughs at the piquancy.

''Having worked in the republic now I have to recognise that there is a great maturity there today. Dublin is showing tremendous willingness to approach and understand, and much of that has to do with self-confidence. To listen to the other side - to find out what their problem is - that's a great thing to do, you know.''

Like Ervine, Mitchell also believes that over generations the Province's established politicians have served the loyalist working class disastrously. ''Those who have represented us have actually turned other people's interest away, stopped them thinking about us. So, we react defensively to everything. It's like in football: everybody loves to see a team attack, attack, attack to try to achieve something.''

In cultural terms, he says, that's become the adventurous strategy of nationalists. ''It's very attractive, very exciting, and along the way they create wonderful things. But we don't do anything like that because we're negative all the time. No surrender . . . as a result there's a deeply worrying sense of rejection.''

So trust and mistrust have formed a crippled hybrid of futility. Yet, when Mitchell heard the news of Rosemary Nelson's death last Monday, what was his reaction? ''Shock. And then a realisation of the difference between news values in Northern Ireland and on the mainland. Here, The Troubles disappear off the news for weeks and suddenly they come back with a major incident. Back home people are killed on a regular basis, and the punishment beatings are every day, but over here you don't learn about that because there's not an important person involved.''

Yet the hatred that propels the bully and horrific acts is precisely what Mitchell's work explores. ''I'm writing about the kind of mindset that creates people like that. There's no point saying to those loyalists: 'You've done a terrible thing, you're terrible people.' We know that doesn't work. But drama can be hugely powerful, although my primary objective is really to entertain people, and I think the work benefits from that. If people are entertained they'll think more about what you're saying.'' And that, of course, might be Gary Mitchell's greatest personal act of trust and service. A stoic's belief that, in the end, truth finds fiction, in all its guises, a more effective messenger than fact.

n Trust runs at the Royal Court Upstairs until April 3.