Playing the double role of a swashbuckling Irish property developer brought face to face with his long-lost impoverished twin brother, Brendan Gleeson personifies the contradictions of a perpetually gridlocked homeless Dublin of glittering apartment blocks, vomiting Temple Bar hen parties and chaotic trolley-clogged emergency wards. The Tiger's Tail is a triple whammy of sex, lies and devilish twists in which Boorman deftly applies a darkly surreal scalpel to Ireland's poor-rich divide. Sardonic humour cuts through the double talk and hypocrisy. An inner city priest, played by Ciaran Hinds, describes the high toll of teen suicide attempts as "suicide bombers protesting against what we have become." Gleeson's character Liam O'Leary jokes that "the more homes you build, the more homeless there are."

Already The Tiger's Tale has received a standing ovation at the San Sebastian Film Festival and enthusiastic reviews in Variety and Screen International. Following its packed premiere at the Dublin Savoy last Sunday . . . in aid of the Irish Motor Neurone Disease Association . . . it seems set to cause a stir when it opens nationwide on 10 November.

Seventy-three-year-old John Boorman is ideally suited to cast a questioning eye over booming getrich-quick, often uncaring Ireland.

He is an English-born outsider who has chosen to live here since 1970 when he and his then wife Christel . . . soon after the success of his breakthrough thriller Point Blank . . . impulsively bought an old presbytery at Annamoe in the Wicklow hills. There he encouraged Neil Jordan and Jim Sheridan to become directors and with his medieval epic Excalibur, filmed on location nearby, he introduced Liam Neeson, Gabriel Byrne, Ciaran Hinds and several other actors to international audiences. He gave Brendan Gleeson his screen break by casting him as the assassinated Dublin gangster Martin Cahill in the Cannes awardwinning The General. Without Boorman, who put Ardmore studios back on its feet and was chairman of the first Irish Film Board, there probably would have been no Irish film industry.

"I see The Tiger's Tail as a companion piece to The General, " he tells me over lunch at the Roundwood Inn. "If Martin Cahill was around today he'd probably be a property developer rather than a gangster. It's much more profitable."

He recalls showing a draft of the script to a leading property developer. "He challenged me on the opening sequence, where Brendan talks about fixing a minister, " says Boorman. "'Oh no, ' he said, 'it's all wrong. You'd never do that, you'd never do that on a mobile phone.'" He got the idea of a story about identical twins separated at birth . . .

one now a tough ruthless developer, the other an alcoholic bum . . .

from a BBC documentary over 20 years ago in which reunited twins were brought together and interviewed. "It was incredible how they'd lived parallel lives, marrying similar partners, doing almost the same jobs and even dressing alike. Since my son Charley and daughter Daisy are twins, I've always been fascinated by how they are so alike and yet so utterly different, so I wrote a treatment and talked to Jack Nicholson about it, because we wanted to do a movie together. He was intrigued, but nothing came of it then. Meanwhile I'd been making notes about contemporary Ireland and wanted to do a film here that wasn't about the IRA. I just wanted to catch a snapshot of Ireland today. So I put the two ideas together and got The Tiger's Tail."

The Tiger's Tail is his second attempt at a movie about a Dublin property developer. Where The Heart Is, his little-seen 1990 comedy written in collaboration with his eldest daughter Telsche, was originally about a Dublin property developer and his wife who in desperation lock their pampered twentysomething children out of the house because they don't want to leave home. "We were actually building the set at Ardmore when the financing collapsed, " he says.

"Eventually Disney Studios stepped in, but insisted on switching the setting to New York."

He wrote The Tiger's Tail in three weeks. "My thoughts about it had been there so long that it all came out very quickly, " he says.

"What I was trying to say, if I was saying anything at all, was about identity. Brendan's character comes to question his whole identity, and that's what Ireland is doing at the moment. There's an identity crisis. We all play a role that we find is successful or interesting and eventually when we try to find the person who we are we find that he is no longer there.

We've become the person we pretend to be. Right at the heart of this is role playing. In the film, you have an actor pretending to be this person who is pretending to be someone else. I really enjoyed playing around with that. If you can be somebody else, does that mean the person you were is no longer there? It's like when kids go to school in Ireland, they spend time learning Irish and religion but at the end of it they don't believe in God and they can't speak Irish.

"I find it fascinating what's happening in Ireland. There's so much that is great in the way it has developed. Yet it seems to be out of hand. It's galloping off somewhere we don't know where. We've all got the tiger by the tail, and daren't let go because God knows what will happen."

Boorman knows all about the confusion of being a fish out of water. Although born a Protestant, his mother sent him to school with the Jesuits. "On Sundays I was in a choir in a Protestant church and during the week I was in a Catholic school, where Father Maguire was a big influence on me and later became a lifelong friend. I was troubled by the two brands of religion, each certain that they were the true religion. And then I had this wonderful epiphany. I was in my little boat on the Thames, which is where I loved to be, saying to myself well they both can't be right, so one of them must be wrong. And then I thought, well suppose they're both wrong. And suddenly this weight lifted from me, almost floating above me, and I was there in nature, where I belonged. That was the end of Christianity for me. When I look at the world today and see how damaged it is, I blame it all on Abraham. He's the source of Islam, Christianity and Judaism, and those three religions have f**ked up the whole world."

Annamoe became a home away from home for many of Boorman's Hollywood friends in the 1970s.

"Father Maguire used come and stay with me as well, " he says. "He'd say mass every day in Roundwood.

And I'd be his altar boy."

Charlie Haughey became a friend. "He was a fixer, " Boorman says. "You could call him up. I got drunk with him a few times. He had a tremendous arrogance. I said to him once, 'Don't you ever feel like acknowledging your mistakes?' 'I can't do wrong, ' he replied, 'because I am Ireland.' He believed that."

When Ingmar Bergman was arrested in Sweden for taxes, Boorman, as chairman of Ardmore studios, wrote to him to offer sanctuary in Ireland. "He was very touched, " Boorman remembers.

"He sent me a beautiful letter saying he'd always had a regard for Ireland, particularly its struggle against colonialism. But he'd already decided to go to Germany, where he made The Serpent's Egg."

Since shooting his ecological thriller The Emerald Forest in Brazil's rainforests, Boorman has been planting broad-leaf oak trees in Annamoe, gradually turning it back into the forest it once was. "I have one or two that I planted as acorns that are now 40 feet high. I must have planted 20,000 by now.

They don't all succeed. Some of them have to go."

Right now he's waiting for the leaves to drop so that he can do some thinning. "When you think of the enormous amount of energy you need to produce hydrogen and how hugely expensive it is, yet trees can do it with ease. They can separate carbon from oxygen.

They can do all these chemical jobs. An oak tree purifies gallons of water every day. The solutions of nature are so simple and so beautiful. This is a tree planet, but we've mostly got rid of the trees. Without trees, the planet cannot survive." He feels a responsibility for his trees. "More than anything, taking care of them is probably what keeps me in Annamoe. I couldn't entrust them to anybody else."

Talking to property developers and very rich people has made him wonder why they never have enough. "Why do you keep doing it, I ask; why do you want more money? They never really answer.

Because it's not the money, it's the kill they enjoy. It's totally obsessive. They can't give it up. They have a compulsion to risk everything, to put all their chips on the one number. And of course at the moment it works. It can't go wrong because property values are going up all the time. But a lot of them have a fall coming."