Women are really dreadfully complicated, aren't they?" says a character in The Norman Conquests, "or do I mean human beings?" The comment, made by a socially inept vet in the third play in the trilogy, could serve as some kind of epigraph to the work of Britain's most popular and prolific playwright, Alan Ayckbourn. He's Sir Alan, actually, but let's not get distracted with visions of staged boardroom aggression. For here – in the hands of the master of the not-so-light comedy – the aggression, and the neurosis, the misery, and the envy, doesn't feel staged at all. It feels, as Ian, the co-proprietor of Interludes guest house in Scarborough says, like "the human condition".The cabbie who picks me up at Scarborough station doesn't use those words, but he does go to the theatre and does, he says, "like a comedy". So does the cabbie who takes me to the Stephen Joseph Theatre (though he prefers, he tells me, with Yorkshire bluffness, "that other bloke, what's his name? Barry Rutter") and so do Jackie and David, my fellow guests at breakfast. "Oh yes, we come up two or three times a year to see an Ayckbourn," Jackie tells me over her scrambled eggs. "We have a rule," adds Ian's partner, Bob, as he comes in with fresh toast, "that we don't discuss the plots over breakfast."
This, after all, is the second most performed playwright in the world after Shakespeare, the most performed ever in his own lifetime, the author of 72 plays translated into more than 30 languages and – quite a feat for a creator of plays, as opposed to musicals – a multi-millionaire. And this morning the multi-millionaire is wearing a bright yellow T-shirt. It's in quite startling contrast to the plush splendour of his enormous home – three houses knocked together – which is, appropriately enough for a man dubbed "the Molière of the middle classes", all polished wood, gleaming glass and fitted carpets. None of your Hampstead faux-Bohemia and distressed floorboards here, the house says firmly. This is Scarborough. We call a spade a spade and we call success, well, success.
Ayckbourn is still moving slowly after the stroke that struck during a trip to an osteopath two and a half years ago. "At first, I got my 'yes' and 'no' mixed up," he tells me, "and I still find when people ask me multiple questions I get a bit confused." If so, there is no sign of it. The slightly gnome-like figure before me is avuncular, genial, fluent and, yes, funny. If, over the near half-century of his career, he has wearied of grillings on the catharsis of comedy etc, he is polite enough not to show it. And if he is, for the first time, grappling with the physical constraints of being (let's face it) an ageing human, his energy is clearly undimmed.
"Yes, they've done a great job!" he enthuses, when I ask him about the Matthew Warchus production of The Norman Conquests at the Old Vic. "[The actor] Stephen Mangan has," he adds, "got all the dimensions, being, as far as I could judge, pretty sexy."
Er, yes. After three evenings watching Mangan's shambling, bearded Norman respectively seducing all three of the miserable suburban women in Ayckbourn's most famous work, I can testify to his charms. "I'm magnetic!" he announces with a twinkle at one point, and every woman in the audience can only agree and sigh. At first, I was worried that the plays – first performed in 1973, with a cast that included Penelope Keith, Felicity Kendal and Michael Gambon – would have dated, but within minutes of being catapulted (which is how you feel when you see theatre in the round) into the dining-room setting of the first one, it was triumphantly clear that it hadn't.
"We've got to remember to play it sad," Jessica Hynes, who plays Annie, told me in the bar after the performance of the second play, Living Together. And it's true that the pathos of the play emerges much more strongly than in that earlier, landmark production, or at least its TV follow-up.
"Reg and Sarah's marriage really makes sense for me," says Ayckbourn. "Paul Ritter is wonderful as Reg and Amanda Root's Sarah is much more vulnerable than Penelope Keith's." Vulnerablility, in fact, is the most striking quality about all the characters in The Norman Conquests: Tom, the excruciatingly awkward bachelor vet; Annie the dutiful daughter who spends her life catering to the whims of a fragile, tyrannical mother; Reg, the hen-pecked estate agent; Sarah, his martyred, gimlet-eyed wife; and Ruth, the vain, workaholic wife of charming, shameless, wide-eyed librarian-turned-serial-seducer, Norman. You want to slap them all. You also want to hug them.
Amazingly, it's the first West End performance for 35 years. It started with a phone call from the Old Vic's resident star, Kevin Spacey, and a lunch with Matthew Warchus at Ayckbourn's house.
"I had a sort of OK on the casting, but I had very little to do," says Ayckbourn. "The choice of the round was sort of quite significant." Indeed. Since arriving in Scarborough as an 18-year-old actor, and working under the theatre director who became his mentor, Stephen Joseph, Ayckbourn has been passionate about theatre in the round.
"If you're looking at another character," he says, "you can see the lady with the bag of chips, and the man who's asleep, so you're never allowed to forget them. Also, you're looking at actions that, despite being funny, you can see the darkness in. And the round is perfect for me, that exploration of darkness and light.
"I learnt very early," he goes on, "that the longer you draw your shadows, the brighter your light becomes and the better your laughter. In rep, when you did a comedy, you put every single light in the theatre up to full and played the pieces very loud and very brightly and very fast. The serious plays, on the other hand, you took all the lights down and played much more slowly, and much more quietly. "Even then, when I was considering a playwriting career, I thought I'd love to write a comedy where all the lights are low and everyone was very slow and very quiet. If I've done anything, I've helped in that movement to draw these strands back together."
You can say that again. The young man who wrote his first play on a challenge from Joseph, and who, after a spell as a radio-drama producer for the BBC, went on to become artistic director and chief playwright-in-residence for what's now called the Stephen Joseph theatre (a post from which he's retiring in the spring after 37 years) has been churning out comedies at about the same rate as the Norman Conquests' Sarah might knock up a casserole. The assumption, of course, is that quality cannot equal quantity and also that comedy equals light. Both assumptions, as it happens, are false. If the 72 plays are not all as glitteringly brilliant as each other, that's to be expected. But glitteringly brilliant is, at their best, exactly what they are. And only someone who hasn't seen an Ayckbourn play could call them "light".
"It's probably true that my work has got progressively darker," he says. "In fact, I stopped calling them comedies, just 'a play by'. A play like Woman in Mind, for example, has a very sharp downward curve of temperature. I remember asking Julia Mackenzie to do it, and she said: 'It's so awfully sad, I don't know whether I can do it.'"
Woman in Mind is, indeed, "awfully sad". In the current production, at the Stephen Joseph theatre, Janie Dee is sexily vulnerable as the vicar's wife who seeks retreat from the misery of her marriage into the (psychotic) world of her imagination. Critics have assumed that the play draws on Ayckbourn's own experience of his mother, whose blurring of the boundaries between fiction and reality wasn't limited to her writing for women's magazines, but actually it's more personal. "She does have quite a prevalent fantasy world going on, which is not a million miles from writing. I'm well aware," he confesses, "when social life gets tough, of using the old writer's excuse and running away. I carried on playing with my toy soldiers until very late, actually, 14, 15, 16. My soldiers had long since discarded their rifles. They were now into quite serious relationships."
Which, it has to be said, is something of an achievement, given Ayckbourn's own early exposure to relationships. His father, a violinist with the London Symphony Orchestra, ran off with the second violinist when he was six. Later, he discovered that his parents had never been married to each other, and that his mother had, actually, been married to someone else. She divorced this husband to marry a bank manager, who she left a few years later. Little wonder that, seeking stability after being packed off to boarding school, Ayckbourn married, at 19, pretty much the first woman he met. The marriage was not a success. He left this wife, Christine after seven years and started a relationship with fellow actor, Heather Stoney. He didn't divorce Christine until 1997, when he finally married Heather. The result, with a rather satisfying Ayckbourn-esque symmetry, is that there are two Lady Ayckbourns.
Nobody, as Joe E Brown's character says in Some Like it Hot, is perfect, but it still falls pretty far short of the unutterable misery that is the state of marriage in much of Ayckbourn's work. "Well," says Ayckbourn, "quite a lot of me is a playwright, and you don't write about happy marriages. They don't make good theatre." I suppose not. In fact, Ayckbourn's work is as much about social attitudes, and the struggles of individuals in particular (middle-class) settings, as about individual human misery. He has compared his political stance to Jane Austen's in relation to the Napoleonic wars (ie disengaged to the point of invisible) but there's no doubt that his work is political in the broadest sense. Mark Ravenhill, not known for his love of light comedy, called A Small Family Business, which is set on the crest of the Thatcherite entrepreneurial wave, the most important political play of the Eighties.
There has, in fact, been a lot of snobbery about Ayckbourn's work. Penguin and Faber initially refused to publish him. Middle-class theatre-critics desperate to escape their suburban roots have sneered at the narrowness of his little-bit-of-ivory palate. Perhaps it's a shame that he has, even in the saddest of plays, always insisted on laughter. Perhaps, without the "comedy" label, he would have had more critical, as well as popular, acclaim. But this, after all, is a playwright who is triumphantly, consummately, deliciously, English. "I'm very frightened of getting maudlin," he says. "I hate being got at. My belief is that people at their most tragic are often at their most comic."
It's true. It's also true that in depicting human unhappiness he has made an awful lot of people happy. "Will that do?" I ask him. Ayckbourn's face lights up. "That," he says, "will do nicely."
The Norman Conquests runs at the Old Vic, London SE1 (0870 060 6628) to 20 December