Many images leap to mind when you think of "the Irish in London", but when it comes to theatre, you may as well be talking about the (ideal) Irish soccer team. With each successive hit - particularly Sebastian Barry's Steward Of Christendom, or more recently, the prolific arrivals of Martin McDonagh and Conor McPherson - it became such a catch-cry in the London media that one critic crowed after a production earlier this year that at last it was possible for someone to write a bad Irish play.

So, for every vogue, there is a backlash. But behind the successes of recent years, the London stage has always had its "bit of Irish" - Wilde, Shaw, O'Casey, Yeats, through Behan, to the eternal Friel, John B. Keane (Ben Barnes's production of Sive is soon transferring from the Watford Palace to the Tricycle), Frank McGuinness, Anne Devlin and Tom Murphy. While such behemoths may have opened up new audiences in the National and the RSC, the mid-1980s saw London sensitised through its prestigious new-writing theatres to Billy Roche's Wexford Trilogy and Ron Hutchinson's Rat In The Skull, and indeed Druid's blistering Playboy. The 1990s wave has seen Irish companies across the board - the Abbey (Marina Carr's Portia Coughlan), Druid (assisted by Garry Hynes's associate directorship at the Royal Court), Rough Magic (with Declan Hughes Digging For Fire, and Gina Moxley's Danti- Dan), Pigsback-now-Fishamble (with Joseph O'Connor's Red Roses And Petrol), Passion Machine (with Paul Mercier's Buddleia) - until this year, it has all become something of a flood: Enda Walsh/Corcadorca's Disco Pigs (soon transferring to the Arts Theatre, while the Bush has commissioned another show from the company); Tinderbox/Darragh Carville's Language Roulette and Hilary Fannin's Mackerel Sky - the list goes on and on.

Among the new writing theatres, the Tricycle has long had an association with Irish work. Its director of 13 years, Nicholas Kent, says: "The Irish have had their richest season in many years, and their ongoing success has to do with the unconventional writing, and indeed acting, styles. Perhaps it differs from English work in that it's not preoccupied with class. But it's got that energy, the youth, the inherent satire - and the new cutting-edge work is a sea change away from the older, more nostalgic material."

He checklists influential shows of recent years - Michael Harding's Una Pooka, Bill Morrison's Love Song For Ulster, Vincent Woods's The Black Pig's Dyke, The Mai - but also Riverdance and Lord Of The Dance. So are the audiences London-Irish or more general?

"Well, we're situated here in `Co Kilburn', so it's certainly part of our constituency but it's far from the sum total."

Closer to the West End, literary manager of the 250-seat Donmar Warehouse (currently running Frank McGuinness's adaptation of Electra), Lucy Davis would reckon that yes, London-Irish audiences come to see Irish work. "But somehow, the Irish shows have nearly all been real hits: Buddleia for the sheer ambition of it, our co-production with Rough Magic of Pentecost . . ."

She, too, would worry about audiences becoming "Irished out, particularly if people twig patterns. A lot of the work has similar themes - although phrased in completely different ways. It's often elegiac, nostalgic, family-based, often rural and concerned with exile. But that said, things are changing quite a bit."

At the Royal Court this year, Conor McPherson's The Weir made such an impression in its 60-seat studio, that it is transferring to the Duke of York's in February for a six-week run. Its literary manager, Graham Whybrow, says: "There is a huge enthusiasm here for the quality, individualism and diversity of Irish work, but it's a deep history, even within the Royal Court, from premiering Shaw in 1904, to End Game, Happy Days and Not I in 1956." He reels off another list of playwrights from more recent years: Tom McIntyre, Mary O'Malley, Tom Kilroy, Pat McCabe, Tom Murphy, Billy Roche and Brian Friel . . .

The upstairs space, of course, also staged the premiere ered of The Steward Of Christendom (co-produced with Max Stafford Clarke's Out of Joint company, which opens Barry's latest play, Our Lady Of Sligo at the National next April). It has also directly commissioned playwrights such as Marina Carr and McPherson. "I'd be hard put to generalise about Irish work, except to say that what we see of it tends to be very, very good - and the Irish have won the roll call of awards. The amazing thing about Irish work is that it can travel so well, despite being so rooted in an idiom and a world. Someone is currently translating Portia into German, but how they're going to deal with the a Co Offaly dialect is anyone's guess," says Whybrow. ere in the 1980s, and since then, it has hosted Rough Magic, John Crowley's True Lines, McPherson's This Lime Tree Bower and St Nicholas and this year, Disco Pigs and Mackerel Sky. "We don't have a particularly Irish agenda here, we just put on good plays, but it just happens that Irish theatre is producing some of the best work. It's had tremendous exposure recently, which makes it fashionable, or to use that awful word, sexy. But the danger is, it might hit a slump." It remains an anomaly that so much Irish work goes into London, without the obverse being true. While the Abbey can afford far better commissions than most of the London new writing houses, Dublin can be problematic for new work, with smaller audiences and a severe venue problem. Siobhan Bourke, administrator of Rough Magic, which first toured to London in 1991, stressed the city's benefits - receptive audiences and theatres (underpinned by their invaluable literary managers); and for playwrights, directors and actors, the multiple knock-ons in terms of other work, international deals, publication, etc. "There is a pecking order for the critics," she says, "but in the new writing theatres, half the audience is the business, literary and casting agents, publishers, so something is bound to come out of it." Garry Hynes is just as pragmatic. "When we went to London first, it was regarded as unusual, but it's simply that we live in and work in an international business now, whether you're talking about actors, directors or designers. And at the moment, Irish writers are producing the work everyone wants to see."

Billy Roche, now under commission to Druid (with a play that will undoubtedly have a London life), has another play, entitled Haberdashery, doing the rounds: "One theory for the success of Irish work is the way the Irish always speak to one another, even if there's daggers drawn." Did he ever find himself tailoring his work for a London audience? "No, no way. As an actor, I try to be just that little bit more distinct vocally, but you have to be true to yourself. Anyone can figure out something that's fake."

But there must be some difference between the audiences? ["]Oh sure. When Cavalcaders went from the Peacock to London, the first night it died totally. There was complete silence where normally there were huge laughs. But the second night we got the measure of them. I remember meeting a couple in London who'd seen one of my plays, and I was concerned how much they had understood, and the guy said, ["]i didn't understand all the language, but I knew what you meant...["] Passion Machine's Paul Mercier's has mixed feelings about London, having toured Studs, Buddleia and Kitchen Sink. "You have to work hard to meet your audience, to figure out the ignition moments, to recognise the cultural differences. As for London being a horizon city, I resist that. It can be a first connection to places all over the world, but having taken Buddleia to Poland, I found that there was this whole other culture, companies from all over, doing their own thing as if the West End didn't exist. "I hate the fact that you can get more kudos from playing a 50-seater in London than playing a 1,000-seater here, I think there's a great danger in looking at London all the time, because you begin to lose sight of your home audience - and let's face it, they've been dwindling. They're there alright, but they're going to the cinema."

With I Went Down, directed by Paddy Breathnach, Conor McPherson has been looking in that direction. But having worked hands-on in Dublin theatre, how does he find London? ["]There's so much more confidence there in new writing, simply as a consequence of the market. I used to look at audiences coming in and wonder where they were coming from.["] ["] You really taking a risk with a new play in Dublin. I just find with a London audience, they're so enthusiastic, they're not just sitting there with their arms folded waiting to be impressed, they're listening. In Dublin, I always find it takes ten minutes for the audience to settle down, stop shifting and coughing. But at the end of the day, I want my stuff to be shown here.["]

Sebastian Barry too - though he would have great loyalty to the Abbey - looks mainly to London. "It's an enormous arena, a gateway to Europe and the world, and I think writers who haven't taken advantage of that have suffered." It still rankles with him that an early invitation from the Royal Court for one of his plays was not also taken up by the Abbey.

["] Having proved oneself here, when you go into London first, it comes as a shock to find your name is blank. I have to say that Billy Roche was a major roadmaker. He came in as an outsider and had hit after hit, but he's very generous, and recommended a number of names to producers over there, including my own.["] Does he ever get the feeling of being better appreciated in London than here? "Well, there was the puzzling and horrible experience of enjoying the revival of the Steward in London, followed by the total panning here of The Only True History Of Lizzie Finn. I don't know, the Peacock is fine but it's very hard to write something big enough for the Abbey stage. It's too diffuse acoustically and every other way.

Next up in the sights is playwright Frank McGuinness's new play, Mutabilitie (his first since The Bird Sanctuary - although he has another new one in the Abbey next year) which opens tonight at the National's Cottesloe Theatre. Having lashed himself to the mast of contemporary history before, Mutabilitie is a typically passionate, allegorical play set in a murderous 1598 in Ireland, and including among the characters the poet Edmund Spenser and his bedraggled visitor, William Shakespeare. "The Irish and the English have a shared history, which is why I'm taking two English literary icons and putting them in an Irish play. While Spenser was in Cork he wrote a dissertation on Ireland, and there were some horrific assertions about the Irish in it, but you can feel behind it, it's a troubled volume; there's still the poet in him. So from the wars of 1598, I'm reaching forward to today with the Irish file's cry to end the war. We're living in a dangerous time, the play expresses that desire we want an end to this violence . . ." Many of the production personnel are Irish. Directed by Trevor Nunn, it is designed by Monica Frawley with music by Shaun Davey and cast with Alison McKenna, Frances Tomelty, Conor McDermottroe and Sean Campion. But how does McGuinness see the differences between audiences?

"Well, in Ireland, they get the jokes quicker, but I think a similarity between the two audiences is that they're both ready to weep." We await the critics' response.