It is the perennial question with which women have tortured themselves since time immemorial: why, exactly, do men cheat? Why do seemingly supportive partners, who had all the hallmarks of loyal marriage material during the courtship period, become serial philanderers once the gold band is in place?
"It's simple," says Peadar De Burca, the playwright and comedian. "It's because they can. Or, rather, because you ladies let them think that they can. So they do."
Harsh words I hear you say. De Burca, however, has a wealth of research -- gleaned at the coalface -- to illustrate his assertion. He is not, one hastens to add, one of the aforementioned unfaithful (married to Wanda just one year and the proud father of three-month-old Lilly Lola).
Instead, he has spent the past five years teasing out doleful tales from 250 men who wander, and 60 women who have endured their husbands' dalliances.
From this Thursday, De Burca will present a comic monologue at the Edinburgh Fringe entitled: Why Men Cheat, an uproarious and, at times, poignant show that lays bare the aims and origins of male infidelity. The show has been staged successfully here in Ireland for the best part of five years.
"Sadly, my conclusion has been that, all too often women simply won't challenge their cheating men," he says with a shake of the head. "Or their self-esteem has been so battered by their husband's behaviour that these talented, attractive and intelligent women convince themselves that they have too much to lose if they walk away or show him the door."
De Burca is a comedy writer who originally found success as a playwright adapting popular films for the stage, including Quentin Tarantino's Reservoir Dogs and Pulp Fiction, as well as When Harry Met Sally and Chitty Chitty Bang Bang.
The author comes from a long line of philanderers, and has a healthy respect for monogamy.
But he became fascinated by the subject when it ripped apart marriages within his own family circle.
"Witnessing the pain some of my female relatives suffered was heartbreaking. The effect was that, from early on, I swore I was never going to become one of those men."
So he set out to investigate the subject, amassing a wealth of hilarious though thought-provoking stories from men who cheat.
Encouraging philanderers to spill the beans wasn't much of a challenge, he says. "Get men to talk about their extramarital exploits? Get them not to talk would be harder," he says.
"Never underestimate the male ego. Men just love to boast of their conquests. Call out the word 'cheat' on any street and a dozen guilty men will look furtively over their shoulder.
'Yet of the women I spoke to, all but three forgave their husbands and took them back. Which was, of course, a green light to the men. My advice to women? Show your confidence. Let him know he's lucky to have you. And that if he abuses your trust, he's out."
De Burca's interviewees cross the social divide and encompass all age groups. (Beware doctors, by the way. They are by far the most likely to cheat, he says. A legacy, he believes, of the fact that they are surrounded by females at work and that women are susceptible to their role as healers.)
Some of the stories, he says, defied belief. Such as the cheating lawyer who proudly boasted that, on being found out, he made his wife feel so bad -- because he claimed he cheated because he had no choice -- that she ended up apologising.
"He told her that he had found solace elsewhere because she had become cold, sex was no longer as regular as it once was, and he had found affection elsewhere. He came back to me saying she now felt so guilty that she kept apologising to him. You can't believe how arrogant he was about it. And, of course, it was carte blanche to continue.''
Another of De Burca's interviewees, a business executive with a big bank balance but few social graces and little in the way of good looks, said he had juggled eight mistresses and made weekly visits to swingers' parties.
"I found it hard to get under his skin," De Burca admits. "I couldn't pin him down as to why he needed to do all this cheating. Eventually, he lost his rag and he blurted out: 'Look I cheat. I have to. Otherwise I'm dead.'"
And therein, says the playwright, lies the answer.
"This man had little in the way of self-esteem. His coterie of young women were his way of reassuring himself that he had lost none of his potency.
"Not in the sexual sense but in the power sense. Having these women on his arm helped him convince himself he was someone to be reckoned with.
"By the same token, had his long-suffering wife cheated he would have been devastated. That would have totally shattered his fragile ego."
Like all artists, De Burca has suffered for art. Literally. One of the sketches in his show is a spoof of an American "relationship guru" he once met at a men's group. The guru loftily told his audience that they had a right to cheat and should cuckold their wives before they did it to them.
'I was imitating him at one of my shows and a woman in the audience thought I meant what I was saying," he explains. "She stood up, told me I was a bastard and thumped me on the nose. She had to be dragged away by security guards while I bled all over my audience."
De Burca (36), who lives in Galway, says his research has made him thoroughly ashamed of his sex.
"Men who cheat come across as though they lead glamorous, colourful lives. They all think they are James Bond. Instead, they are romancing women who are generally diluted, poor substitutes for the wives they have at home. The reality is that their lives are seedy. Full of pitiful skulduggery."
By contrast the women De Burca spoke to invariably felt they could not face breaking up the family.
'So many strong, beautiful women told me they would end up alone and lonely if they threw out their cheating husbands. There was one, in particular, who asked me to accompany her while she trailed her husband and his new mistress.
"We would sit for hours outside the other woman's home while he was inside. The wife wept but couldn't stop following him.
"Yet she steadfastly refused to confront him. She made the usual excuses, but the truth was that if she confronted him she would have to do something about it: make decisions.
"Like so many, she couldn't face that. But, unlike her unfaithful husband, who felt no guilt, she was torturing herself. She desperately needed to know why."
De Burca often spots the interviewees in his audience. "That can be incredibly funny in a sad way. There he will be, sitting alongside his wife, chortling away. He probably thinks she hasn't a clue it is her husband the anecdote is about. He, however, is the fool. Believe me, nine times out of 10, a woman knows."
And what of women who cheat? Are their reasons any different? "Not noticeably," he says laughing. "The difference between the sexes where infidelity is concerned is that women are just a whole lot better at it. When women cheat, they do it in style. And they don't get caught."
Why Men Cheat by Peadar De Burca is at the Assembly Rooms, Edinburgh, from August 5 to 30