The singer has sung Paddy Reilly, When Irish Eyes are Smiling, and "the most requested song in the world", Danny Boy - all with an obvious Irish accent. She sounds like Maureen O'Hara. It is a gentle routine and everyone seems more than happy as the little man in the white dinner jacket and green-and-white bow tie comes on stage.

The photographs on the walls are of Hollywood legends: Jimmy Stewart, Clark Gable, Ingrid Bergman and a moody looking Judy Garland. A couple of busloads of American tourists have finished their meal, during which the background music was dominated by the best of Andrew Lloyd Webber, and are waiting for the main act. The mood is unmistakably Irish - or at least that of Irish cabaret as frequented by non-Irish patrons. Up on the stage a large Tara brooch illuminates the back wall. Irish dancers will appear after the interval.

Monday night in the Celebrity Room at Dublin's Regency Hotel and veteran comedian Hal Roach prepares to do what he has been doing for almost 60 years: telling gags. No props, no straight man. He looks as if he is enjoying himself and certainly looks a lot happier on stage than he does off it. At the entrance to the venue there is a display of sorts featuring show posters, such as Gaels of Laughter (1976) with Maureen Potter, and various awards including one for Services to Irish Tourism.

His routine is not going to offend or embarrass. There is are no sex jokes nor are there gags about politicians. It seems a shame not to be able to avail of the ongoing comedy called Tribunal Ireland, but his audience is American and Roach wants them to think the Irish are good at laughing at themselves. His picture is that of a nice place populated by amusing people. There is no nastiness, either, in his Ireland or in his material.

"A man sees a beautiful widow woman and he goes up to her. `I've been watching you and I want you for my wife.' The woman replies: `What would your wife want me for?' " Another man buys a jigsaw puzzle with eight pieces. Nine months later he has managed to put it all together and is delighted with himself. He thinks he has done well. `On the box it says four to six years.' "

The jokes continue - well travelled but well delivered. Everyone laughs and Roach repeatedly throws in his well-worn catchphrase: "That's a good one - write it down." You want wake jokes? He's got them. He informs the audience that the first three letters of "funeral" spell fun. He knows he has his audience so he is free to extemporise on his theories about humour and laughter as man's saviours.

"To laugh is to understand, to laugh is to forgive" - it could come from a homily but the audience don't mind. There's a righteousness about him; few comics would impose their life theories and values as blatantly, but then Roach does so with the confidence of having learnt to read an audience in a couple of minutes.

Stand-up comics are a vulnerable bunch, at war with their egos. A room must seem very empty if no one is laughing. Part of the technique seems to be that if you don't get the joke, it's really your own fault. "That's all right madam, she'll explain it to you." At intervals throughout the routine Roach pauses and muses: "I'd love to be down there with you listening to this."

Ever meet a happy comedian? Look down a list of names and they certainly are a miserable bunch, all engaged in a lifelong search for approval. Hal Roach does not exude contentment either and says he is not happy: "I don't know why, but I'm not". Take him away from his audience and he is very serious. "I am a private person, I'm shy. What am I - an introverted extrovert or an extroverted introvert? All comics are. You can't make a comedian, you can't teach someone to be funny," he says "comedians are born." A situation then develops wherein these miserable characters have two options, hide from life in a hermit's cave or take to the stage and force strangers to laugh. It all seems extreme. But it is. It seems to be the ultimate therapy session for the comic as much as for his audience seeking laughs.

Hal Roach is wary of being interviewed. He makes that clear. "Let's get this over with as quickly as possible," he says on the phone. A couple of hours later, he is standing on the top of a steep hill near his house in the Dublin mountains. Two cars have just crashed and he is a bewildered onlooker. It takes him a couple of seconds to move on from what he has seen. No one seems hurt, but it's the idea of two cars colliding in a space that's usually empty which is perturbing.

There is a fine view of Dublin from most of the windows in the house. Even on a cloudy day it is possible to see Dun Laoghaire Harbour and Howth Head. "We didn't have much of a view where I grew up in Waterford. Just the view of a brick wall." It was tough in Waterford in those days, he says; times were hard. "Not just for me, for everyone."

Christened John, he was one of five children. There was no money. His father was a labourer and Roach says of himself: "I got very little schooling" - although he did get the nickname Hal, inspired by his likeness to one of the characters in the Our Gang comedies by Hollywood's Hal Roach.

His life was decided when the young John Roach was about 12 and a touring show came to Waterford. There was a talent competition and, although he had entered as a boy soprano, he told a joke and was on his way. He went on tour with the Great Bamboozalem, a magician.

The young Roach watched everything and for a while his own routine was that of a comedian illusionist. It must have been exciting, but were his parents upset at his leaving home at such a young age? "No, it was one less mouth to feed."

He does seem haunted as he sits in an armchair in a room full of career memorabilia recounting the story of his early life. Even allowing for the fact that he is very small, Roach is a frail character with a little face dominated by his glasses. Anxiety is his natural state, he frets about everything. The family dog is an easy-going character with obviously absent-minded tendencies. Roach keeps an eye on him. As for the comedian himself, his performer's voice seems far stronger than it should be. Nine years ago he had cancer and lost half of one lung. Did he think he was going to die? "I did, so I got everything ready. But here I am."

At 71 this self-styled "missionary for humour" has in Ireland always been overshadowed by his success abroad. "Americans, New Zealand, Canadians, Australians, mainly. But I also do cruises and have done a lot in England. The new generation of Irish comedians are doing very well but then everything Irish is currently in a no-lose situation. It seems impossible to fail."

Roach mentions one young Irish comic who appeared on The Late, Late Show with a routine which caused offence. "There were complaints and apologies. Then he went off to Edinburgh and won the comedy prize," he recalls with a shrug that clearly says there is no accounting for taste.

The thought of telling his story does not excite Roach. "I said all this before, everyone knows it" but then he settles down to describing the days of the fit-ups and how he used to sleep in the theatre after the show. He was still a child. If there is a clue to Roach's tense, edgy personality it may be that he never had a childhood. He is not a complainer, though, but his determination to survive and succeed must have left its scars. God, children and humour are his themes.

No one made life easy for him. He had to sell himself the hard way. "I always looked funny," he says thoughtfully. Roach has none of the advantages of a Dave Allen. Probably Ireland's finest comic, Allen has the advantage of looking well in a suit and filtering sophisticated, often daring material through a trademark tone of world weary exasperated outrage. Allen was made for television. Roach had to graft before live audiences and, although he survived several years on the English circuit, he was to first find his American audience in Ireland.

Now in America he can do no wrong. "I've played for five US presidents and I've liked them all. I wouldn't want to be any of them. It's a terrible job". And Roach is yet another Irish person who feels more appreciated abroad than at home. Last St Patrick's Day, he was the Grand Marshal of the Washington parade. When he speaks about the days of variety and music hall he echoes the stories told by Maureen Potter, his near contemporary. The difference is that Potter usually worked with a team, Roach is at his best on his own. In 1983 he received what had come to be regarded as Ireland's version of appearing on the New Year's Honours List - he was the subject of a Late, Late Show lovein.

For him comedy is an art. "It's about timing, delivery, eye contact, your walk, the way you use your hand. The expression on your face. You could give the same joke to 10 different people and only one of them would be able to make it funny. The major weakness of comedy today is the dependence on smut. Say `f--k' and an audience will laugh." He admits to not being a fan of the Father Ted series and says he doesn't like the Simpsons. I must have looked shocked. "When they first appeared, I gave them two weeks," he says, "but you can't argue with success." Of the current generation of comics he praises Rowan Atkinson. "He's very good. He's in the Chaplain mode, he's really a clown. Children like him a lot, he can do anything with his face and his body. He doesn't have to say anything - he is a very funny man." He has other favourites in Buster Keaton, Jackie Gleeson, Hancock and, in particular, Jack Benny "the greatest". Then there's Tommy Cooper, "a genius", and Morecambe and Wise.

At its best, however, US comedy has something special. "But the problem with it is that there is too much of it." He praises the team playing of Cheers and concedes Bob Newhart is funny but adds: "He is more of a comedy actor though." Equally he points to the limitations of the over-the-top frenzy of John Cleese, while agreeing Fawlty Towers remains a classic. Somewhat surprisingly he says he liked Black Adder in its various guises but its writer, Ben Elton, as a performer, epitomises the vicious, aggressive style of comedy Roach most dislikes.

Many of those Roach shared bills with are very famous - "I played with Frank Sinatra, Connie Francis, Vic Damone" - and he witnessed Judy Garland's agonies at their most intense. "She was so unhappy, a very sad lady - there were so many problems. But once she went on, you could forgive her anything."

How much could he forgive Lenny Bruce, the first of the blue comics? Roach knows what Bruce was trying to do but disapproves of the material. "He was pornographic. That's one thing about me - I'm clean, there's no dirt." He writes most of his material himself: "I see myself as a writer, I've written books of comedy."

Memories cover the walls of the small living-room. Among the few books is one about Peter Cook, another miserable genius. There is a picture of his wife Mary (whom he married in 1951) and her sister as they were in their accordian-playing days. With the life Roach has had, only a fellow performer could have understood.

"Mary's from Dublin, but her mother was a Belfast woman, May. There's a famous Dublin fish and chip shop - Burdocks - she began that in the 1930s. May Burdock. She was great and a real fan of mine, great support. No mother-in-law jokes. I had a great relationship with my mother-in-law." He speaks about the time he and his wife lived with their children in South Africa and the children developed fairly strong accents. They have three daughters while their youngest child, their son John, is the most famous. He has Down's syndrome and, according to Roach: "John has taught all of us a lot. He's the best person I have ever met."

Roach chalked up 28 years in Jury's cabaret in Dublin. He feels those smoke-filled nights must have contributed to his brush with lung cancer. "I used to smoke myself but that was years ago." The illness nine years ago must have changed him but Roach's attitude has probably always had that element of determined defiance. Ever the professional though, his audiences have never witnessed anything other than good humour. When he was in hospital he had to wait until a series of tests decided if he was fit enough to undergo surgery. He was.

At the Regency evenings which he began in May, no smoking is allowed. These cabaret evenings, at which he is acclaimed as "the king of Blarney" are the result of him and promoter Fred O'Donovan deciding "to do something", after Roach had returned from a three-month stint in the US.

One of the best gags of the night is when he reads a series of motor insurance accident reports such as "the pole I hit was obscured by people" or "I had to swerve 10 times before I finally hit the man" or "the bus I hit while reversing out of my driveway was five minutes early".

The Ireland featuring in his act is an amusing place populated by natural comedians who answer questions with questions, smile at death and are gloriously eccentric - no wonder visitors enjoy it so much, while the natives don't seem to recognise the place at all.