IT was more than the long suffering Irish teacher could take two clowns of the class sharing a desk, partners in playing the fool for the entertainment of their fifth year classmates. They were separated and forbidden to sit together again.

That was 2 years ago. Now the two Terenure College "old boys" have been put sitting side by side for the first time since - on stage for the Gate's upcoming production of A Tale of Two Cities. Adapted by Hugh Leonard from the Dickens classic, Stephen Brennan plays the leading role of Sidney Carton and his former schoolmate, Philip O'Sullivan, is alongside him once more as a legal colleague, Stryver.

There is much in the part of Carton - the disillusioned lawyer with the drink problem who goes on to redeem himself by making the ultimate sacrifice for love - that Stephen Brennan identifies with. "He's a character I can relate to in that, basically, he's a shy character - that's part of why he drinks. He is a man of great intelligence and great ability but has never managed to quite fit into the world, so he's given up trying."

The paradox of being shy and being an actor is one which Brennan has struggled with for much of his life. Born into one of the great acting dynasties of Irish theatre, it was almost inevitable he would end up on the stage. His father, the late Denis Brennan, was known as the golden voice of Irish radio and his mother, Daphne Carroll, regularly commandeered the airwaves of Irish kitchens as the petulant Mrs Doyle in Harbour Hotel.

All five children followed their parents' lead into acting: Barbara, Catherine, Paul, Stephen and Jane. In a newspaper interview five years ago, Catherine recalled the young Stephen as: "Very quiet and shy but very funny at the same time, and even though he was a great mimic from a very early age, he used to clam up in front of people so that they wouldn't benefit from his hilarious impressions of friends and relations."

At 41 years of age, sitting back in a chair with his sandal clad feet up on the table in the hospitality room of the Gate, he drags on one of a succession of Dunhill cigarettes and ponders the question of his shyness. It is undoubtedly a factor in why people say Stephen Brennan is a man who's not easy to get to know. It may also account for his reputation as an actor who goes into film interviews with the part in the bag and comes out without it.

"I've consciously fought to break the mould," he says, stretching forward to pull up the grey woolly socks under his blue denim jeans. "I suppose in a way I've ended up not knowing who I am because I kind of adapt to whoever I'm talking to. I don't know why that is, probably an insecurity of some kind. It's probably why I don't get on very well at film interviews. I can't sit down and talk to a stranger. I don't know who they want me to be. I'm just not good at it. I can't relax - no matter what I try to be, I'm trying to be something. I'd rather go and have a jar with someone and let them find out whether they like me or not."

This crisis of identity is a surprising and frank revelation by a man who now occupies such a singular position in the Irish theatre. He excels at the sophisticated, caviar comedy of many of the Gate productions, as opposed to the meat and potatoes variety more often seen at the Abbey. Although he has no contractual obligations - or guarantees - to the Gate, the bulk of his work over the past eight years has been central to the burgeoning success of Michael Colgan's theatrical empire.

Master of the arched eyebrow, the curled lip, the seductive strut, his ability to quietly impose himself on stage marks him out as a premier league player. But the apparently effortless performances don't come without hard grind. "It always annoys me when people come to shows and say `of course you do that kind of thing off the top of your head' and I say `well I'm glad I made it look easy'."

IT'S Saturday afternoon and Brennan is just a couple of hours away from his final performance as the status seeking suburbanite, Paul, in Bernard Farrell's comedy, Stella by Starlight. He was in at nine this morning for a run through of A Tale of Two Cities in front of "the politburo: the office, Michael Colgan and co". And the last three weeks have been like that: rehearsals by day, performance by night. "It really does wear you out.

It certainly doesn't leave much time for the most important role in his life, as father of Sarah (18), Kate (12), Holly (11) and Johnny (4) in their Rathfarnham home. It probably helps that his wife, Martina Stanley who plays Anne Clarke in Fair City, understands the pressures. "I don't know what it would be like married to somebody who's not in the business. There'd be an awful lot of explaining to do."

His idea of relaxation is decorating. "I don't just decorate home, I do other people's houses. I have a builder friend I go and work with sometimes. It's like my therapy; I switch off and just do manual labour." He also paints oils and acrylics: "Lately I've been madly doing paintings of Waiting for Godot". He played Lucky in the Gate's Beckett festival which garnered critical acclaim at the Lincoln Center in News York this summer.

When it comes to parenting, it is another aspect of his life which he consciously compares with his father's. "I do measure most things I do off him," he admits.

"My father ...", he pauses to contemplate how he's going to describe their relationship. "He wasn't there a lot of the time because 1) he was busy and 2) he was an alcoholic, so that made him slightly removed from his children, a bit mysterious.

"When I was a kid I remember walking through the streets with him and heads would turn and say `that's the man with the beard'. Nobody had beards in those days. I was aware of the fame which fascinated me and of which I was quite proud. Unfortunately I don't ever remember seeing him on the stage but I heard him on the radio a lot and saw him on television. He was a very fine actor and it was just a tragedy that his alcoholism got the better of him. He gave his last stage performance before the age of 40 and that left him an even more frustrated man. But he just kept going and when he was fine, he was fine. I was only just getting to know him, we all were, when he died.

"When my father was drinking; there was fear in the house," he recalls of their home in Rathgar, Dublin. The rest of the family bonded in the face of that fear. "My mother is the total opposite, doesn't drink, doesn't smoke, is a very genteel, caring sort of person. We had a very loving family relationship." Of which his father wasn't a part? "He wasn't, a lot of the time, but when he died I realised how much he was.

Brennan sums up his father as one of what Tennessee Williams called "the weak, beautiful people". "He was a beautiful person, a man of great passion and great intelligence and this dreadful problem he had spiked all our lives and made us all grow up and understand human beings a bit more clearly than your average family situation might."

As the son of an alcoholic, he agrees that the spectre of becoming dependent on drink is "always over the shoulder". He explains: "I have been through periods when I have been quite a heavy drinker and thought: `Jaysus, should I go and get myself sorted out?' But I've always come out of them and now I just can't physically hack too much drink and I don't like what it does to me the next day."

Of course all the Brennan children craved their father's professional approval. "We all wanted the imprimatur of the pater, that was important in a way." It was particularly poignant for Stephen when his father went to see him play Hamlet in Michael Bogdanov's unorthodox production at the Abbey in 1983.

"It was his favourite play but he had never got to do Hamlet himself. He had played Horatio to Mac Liammoir and to Cusack. It was the last show he saw before he died, me playing Hamlet."

Donal McCann had sent Brennan a requiem card as a joke on the opening night of Hamlet saying, `sorry to hear about the daddy'. Seven weeks later, Brennan really was burying his father. "I met McCann after my father died and the said, `Oh God, sorry about that'."

AT 27, Brennan was considered to be young to take on Hamlet. "You need to have been about a bit to play it well," he agrees, "and I don't know how well I

played it. I got away with it. It was total fulfilment. When I finished the show every night I felt, `I'm an actor; I have acted'".

It wasn't a bad way to end his eight years as a "company man" with the Abbey. When Bogdanov invited him to join the National Theatre in London for a year, Brennan ditched the permanent and pensionable job and set off to further his theatrical education. But when he was invited to sign up with the RSC after that, he declined. "I had had enough of companies by then. You go in and do four shows, two of which I was interested in doing and two I wasn't, so it would have meant I was spending half my time doing something I didn't want to do."

After nearly five years of London "I couldn't wait to come home". But he had been happy to leave Dublin. "I had got to a certain stage with the work where he was fairly well established as a leading young man. You really need to go away and work with other people and broaden dour experience. Also, I didn't particularly like the country at the time, various referenda upset me a bit.

"But having lived in Margaret Thatcher's Britain for four and a half years, I was absolutely delighted to get back." He also says he found a very different Dublin to the one he had left in 1983.

"There was a new audience coming to the theatre and that was very refreshing. I was coming back to the village. I had missed the sense of community."

He anticipates the next question: "I had no sense of failure comings back. A lot of people think, you went away, you came back, you didn't make it, tough luck. Funnily enough my first starring film role was back here when I came to do Eat the Peach (1986)."

BUT does he think he would have got better breaks if he had hung on in London? "Possibly. But the quality of life comes first and I take it as it comes. I have kind of got over the early ambitions of wanting to be a megastar and I am quite happy that I have made a career out of not being well known."

Yet, cutting a striking, handsome figure at six feet, two inches, he had all the credentials to be a signed up member of the current gang of fortysomething Irish male actors who are, according to Aine O'Connor, "leading Hollywood": Liam Neeson, Gabriel Byrne, Pierce Brosnan, Patrick Bergin, Stephen Rea and Aidan Quinn.

"I say good luck to them. Obviously I would like to be doing some of the work that they do, who wouldn't? But I'm not jealous of their success. They went out specifically to find that and I didn't. I'm just going another route. I might do a Ray McAnally and be discovered when I'm 55 or something. I'm very happy at the moment that I'm connected largely with the theatre that does, I think, consistently produce the highest standard of theatre in this country?"

Why has he done so little work for RTE?

"They don't ask me to work for them. I've been abroad on the odd movie and people there say what are you doing next, going back to make a telly'? I have to explain to them that unfortunately I live in a country where our national television station has absolutely no interest in drama whatsoever. So I'm unlucky, that is an area I miss. I would love to do more television and film."

However he has just completed three episodes of the new BBC series, Ballykissangel, due to go out in January, in which he plays a fading rock star who rolls into town and casts an eye over Dervla Kirwan.

He speculates on why Montrose shows no interest in him: "Either because they're right, that whatever they happen to be doing I'm not right for, or they think I just do posh plays at the Gate and they've forgotten about the 15 years I had before that.

"If there was to be a downside to the last eight years, it's that people tend to think of me as a classical actor who speaks", he adopts a suitably nasal tone, "with a posh voice. Sometimes I feel I am marking time a bit and I want to go on. I'd like to do a bit more with music if possible and other areas I haven't worked in."

Lucky in Waiting for Godot, Petruchio - in The Taming of the Shrew, Frank `n' Furter in The Rocky Horror Show, the title role in Tartuffe, Mr Darcy in Pride and Prejudice, Marlow in She Stoops to Conquer. Lord Henry Wotton in The Picture of Dorian Gray and now A Tale of Two Cities. An impressive way of marking time for a class clown.