Just above my head, a shelf groans with folders containing drafts of unperformed plays. If I twist round, I can make out some of the titles: Euphoria; Pursued by a Bear; A Better Mousetrap. These are not names you will find in any theatre dictionary. Have I penetrated the lair of some crank with a gift for titles and nothing else?
No, this is the work room of Peter Nichols, four times winner of the Evening Standard award, among other gongs, and the walls are bright with posters of his hits. There's Privates on Parade, his hilarious, politically sharp, revue-style account of his time with a military song-and-dance unit in South-east Asia in 1948. Another advertises a mid-Eighties New York revival, starring Jim Dale and Stockard Channing, of A Day in the Death of Joe Egg, his ground-breaking, semi-autobiographical play exploring the strains of raising a severely handicapped child through bitterly funny marital back-chat and painful domestic vaudeville.
And on the wall behind him, depicting a naked, nubile young woman with a cascade of red hair, there's the poster for the original 1981 production of Passion Play, his darkly comic drama about adultery, which is revived this month at the Donmar Warehouse, directed by the rising star Michael Grandage.
Since 1982, though, when Nichols fell out with the RSC over its handling of Poppy - a piece that presents the Opium War between Britain and China as an ironic Victorian pantomime and which Terry Hands tried to produce as a major musical - Nichols has become more famous for being neglected and embittered (vying for top place in the latter category with Arnold Wesker) than for being one of our most penetrating and virtuoso postwar playwrights. Indeed, he once published a long poem in this newspaper, a Coleridge spoof entitled The Rime of the Ancient Dramatist, in which he imagined himself accosting Richard Eyre at a drinks party and "seizing [the] chance to chide him on the rejection of all he hath submitted, so that his plays hath not been seen on the South Bank since the days of the Olde Vic".
But you shouldn't decide what people are like before you meet them - advice I'm indirectly given by the dramatist himself. Kate, the young husband-snatcher in Passion Play, is a photographer, and Nichols has just been photographed for The Independent. I ask him how the steamy Kate would have wanted him to pose, and he side-steps the question by launching into a recollection of being snapped by Snowdon in the early Seventies. The family house in Blackheath had been scrupulously overhauled for the earl's visit. "He took one look at it and said, 'Oh, no, this is much too tidy,' and drove me down to the derelict hospital where they were filming The National Health [his state-of-Britain National Theatre play]. It's amusing really," Nichols says, hunting out the black-and-white photograph in which he appears "looking like something out of Beckett", morosely slumped on a wooden chair with bits of rotten plaster all over the floor. "It looks as if I've just been throwing up. My point is that he knew what he wanted before he came."
Point taken. It's true that there are long sections of our conversation in which you simply would not relate this affable, funny, if slightly chippy man to Ted Forrest, the middle-aged dramatist eaten up with professional resentment in A Piece of My Mind, his dazzling and underrated 1987 play about writers' blocks and jealousies.
I've always felt that Nichols's work has creative affinities with that of Stephen Sondheim (Poppy is, in a sense, his Pacific Overtures), so it's gratifying to learn that they are close chums (Nichols is just back from New York, where Sondheim threw a party for him), that a fan letter about Pacific Overtures started the friendship, and that they have discussed collaborating but have discovered that they are perhaps too alike for such a team-up ever to work.
Nichols is a trained actor, a point made evident as he performs stories about people such as Beryl Reid, who starred in his play Born in the Garden. Her brother, to whom she was close, died on the day of the dress rehearsal, and there was panic over whether she would make it through the first night, especially as she had to confront a coffin in the opening scene. "I said to the rest of the cast, please support her - which they did. And, of course, she sailed through it like a galleon, and the rest of them were like: 'Where are we?'."
He then does a very amusing impersonation of Barry Foster (one of his favourite actors) rehearsing a big downstage speech and wondering whether it was, on the whole, better to have Beryl doing some light dusting behind him or (as she disingenuously suggested) standing stock still. Either way, an audience would not have been able to take its eyes off her.
But it also becomes clear that Nichols's pleasure at the prospect of the revival of Passion Play - at the buzziest of venues, with a beautifully balanced cast and a hot young director - is more than a little tinged with regret that it is not one of the unperformed plays that is being produced.
I'm also more than ever impressed by the truth of Irving Wardle's comment that Nichols is "a man whose profound suspicion of the theatre is the mainspring of his dramatic power". As with the reverse time-sequence in Harold Pinter's Betrayal, and the play-within-a-play tricksiness of Tom Stoppard's The Real Thing, Nichols's adultery drama Passion Play hits on a powerful theatrical device for dramatising the deceptions and treacheries of infidelity.
Having been propositioned by Kate in a restaurant and treated to a taste of her tongue down his throat, James, the male-menopausal picture-restorer, returns home and becomes quite literally two-faced in a double act with his alter ego, who bursts out of a cupboard, alternately reminding him of the details of their alibi and willing him to confess. The moment she discovers the affair, his wife, Eleanor, splits in similar fashion. The metaphor is so simple, so dynamic and so truthfully revealing about the contradictions and self-division in such a troubled relationship, you wonder that no one had thought of it doing it before. But Nichols worries about "theatrical devices becoming an end in themselves".
He's fond of quoting the novelist Henry James, who came a terrible cropper with his play Guy Domville. James said of writing for the stage that "its honour and inspiration are in its difficulty", but also referred to "the hard meagreness of the theatrical form".
Being in two minds about the theatre is complicated for Nichols by a preoccupation with what he calls "the illusions of freedom and the consolations of captivity". He's a dab hand at finding mechanisms for his plays, but are these, he's sometimes inclined to wonder, contraptions that comfortingly confine rather than release? Such qualms are, of course, integral to his great talent.
He's currently writing the book for a musical built around the songs of Hoagy Carmichael. There's hope, too, of persuading Stephanie Cole (like him a native Bristolian) to appear in So Long A Life, a drama about an 85-year-old Bristol woman. Meanwhile, there are the Passion Play rehearsals.
Nichols himself has written that this play "has the property of setting the four main players against each other, probably because they are playing only two characters between them".
This recipe for rehearsal hell sounds like another Nichols comedy in itself. Michael Grandage tells me that one of the cast (which includes Cherie Lunghi, Cheryl Campbell, Martin Jarvis and James Laurenson) read out that quote on the first day of rehearsal and said: "At least let's make a pact that we won't let this happen to us." But there's such cross-fertilisation in the interplay of this quartet, he reports, that after a tricky start, things are now going smoothly.
"I told them", reveals Nichols, "that it's a play that's more difficult to perform than to write, and they said, 'Oh, yes, yes, yes.' And I thought: 'Well, how the hell do you know? You didn't write it!'"
'Passion Play' previews at the Donmar Warehouse, London from Tuesday; 020-7369 1732Reuse content