Indeed, the Tom who opens the front door (with no sign of anxiety) is lean, ebullient and displaying the booming-voiced confidence of a thoroughly outgoing fellow. There isn't a net curtain in sight, and Kempinski stands in front of the large, open windows of his front room, legs apart, staring confidently out, in total contradiction to the cowering neurotic his plays have led us to expect.
He's watching a couple of workmen painting the outside of the house opposite. "There used to be an old vicar living there," he comments, waiting for the kettle to boil. "I hadn't realised he'd died, and one evening I came back and saw two men in the house. I thought they might be intruders, so I took a metal bar - I do pull-ups every morning, and I took the bar I use - and went round to investigate. They got the fright of their lives!" and he laughs contentedly. As a performance aimed to convince a stranger that all traces of the old malaise are gone, it deserves an Oscar.
You get the impression that everything Kempinski does is on a grandiose scale. When he was an actor, he worked obsessively for 11 years, with only 10 months of unemployment in that time. His first play, Duet For One, starring his then wife, Frances De La Tour, was a huge hit (the Bush, the West End, Broadway, performed in 42 countries, a film starring Julie Andrews). His divorce from the actress was widely publicised and very traumatic, precipitating him into an enormous breakdown. At its worst, he allowed himself to be photographed to promote a new play lifting his shirt to reveal the full rotundity of his 24-stone stomach. That play, Sex Please, We're Italian, starring Helen Mirren, was a gigantic flop, attracting some of the most disparaging reviews ever seen. Now that Kempinski has decided to re-invent himself as "cured", of course, it's going to be massive.
And he couldn't quite resist that reference to his new partner. He still has to prove he has got over the woman he refers to even now as "Frankie". He shows me, quite unbidden, photographs of himself and his new partner, Sarah, sitting at a cafe table on holiday in the Dordogne. His pride and delight is such that it's hard not to participate, but even so, 11 plays in two years? Isn't that taking it all a bit too far?
Kempinski has warned me that he talks a lot, that the problem isn't getting stuff out of him, but getting him to stop. And now he's off - telling me about Salus Populi Suprema Lex, which is opening in Glasgow, and Don Quixote and the Jewish Question in Germany, and What a Bleedin' Liberty at Theatre Royal Stratford East, and that Anton Rogers and his wife are reviving Duet for One at the Riverside Studios in the middle of it all, and that Bristol Young Vic are doing another new play in September. He tells me about all the rejection letters he's received, and why the plays were rejected: not because they weren't good plays - none of the letters said that - but people can't always handle his up-front style. And then he tells me what his new therapist has to say about it all: "The plays partly help with feelings of loneliness. They're like a guarantee, a way of ensuring that there's something there for me in years to come," he confesses.
He has an intimate and detailed understanding of all his own defences, reactions and self-deceptions. Until recently, it seemed he was trapped in a purgatorial state whereby he understood both the mechanics of his neurosis and the reasons for its hold on him, yet he was still incapable of freeing himself from it. He was unable to leave the house except to drive the "four point seven miles" to his analyst and walk 70 yards down the road to the shop. Sometimes his phobia of the bathroom meant he couldn't wash for months on end. Separation did not shirk from portraying the controlling, manipulative nature of his own egocentricity. Yet what you see is a man of considerable charm, full of self-knowledge, intelligent and entertainingly witty.
It's hard to tell how tough his confidence really is behind all the bravado, but the brutal question has to be asked: if he's written such a quantity of plays in so short a time, can he really be sure of their quality? The playwright barely pauses in his flow: "I don't want to overstate the speed with which they were written - and, besides, Wilde wrote The Importance of Being Earnest in 17 days and David Storey can write a play in three days, so three-and-a-half weeks is quite a reasonable time for a play. But what has happened is that an awful lot of plays were held back in the last 14 years. All neurotic symptoms are defences against things that are too awful to face, and they stop you doing things. I did do some writing in that time, but now it's really flowing. If I'd started at 20, all these plays would have been spread over 30 years, and it wouldn't seem strange at all." And again, charisma overrides doubt, and you feel empathic joy for the amazing explosion of creativity Kempinski is going through.
Duet for One was the first play successfully to appropriate the psychoanalytic process for theatre. That was written before Kempinski himself went into therapy, but 16 years on, What a Bleedin' Liberty is the only one of the four new plays opening this year that doesn't contain scenes of Kempinski's own therapy sessions. Though it almost certainly accounts for some of the rejection letters he's received from theatres, Kempinski remains doggedly committed to this self-confessional mode.
"Artists like to think that art is magic," he exclaims. "But it's not! It's about personality, conscious and unconscious. People think if they say it's 'just' autobiographical, it lessens it. I think it's the opposite. Of course we use what's in our heads. Where else is it going to come from? Everyone writes autobiographically. Of course it's mediated through thought and craft, but it's all drawn from experience. Don't let them kid you if they say it isn't - it's bullshit. Bullshit!"
n 'What a Bleedin' Liberty' opens at Theatre Royal, Stratford East on 18 April (booking: 0181-534 0310); 'Salus Populi Suprema Lex' opens at Glasgow's Ramshorn Theatre on 2 May (booking: 0141-552 3489); 'Duet for One' opens at the Riverside Studios on 7 May (booking: 0181-741 2255); 'Addicted to Love' opens at the Bristol Old Vic Studio in September