A warning goes out to those visiting Michael Codron. To get to London's longest-serving producer, whose office sits at the very top of the Aldwych Theatre, you have to climb the kind of spiralling stairway that takes you to the top of castles or to the bottom of Tube stations. There are enough steps to take you past many of the framed posters that publicised some of the 200 shows that Codron has put on since he started producing in 1956.
Appropriately enough, Putting It On is the title of Codron's biography. Written in collaboration with the director, Alan Strachan, the book tells the story of a man who was destined to work for one of his Sephardi father's businesses, including a chalk mine near Oxford. True, the job would have been at a desk not the chalk face. But instead, he carved a career as a discoverer of new writing talent to put on in the West End.
Codron, now 80, sits behind a desk which manages to be grand yet not ostentatious. His office walls are a deep red and most of the pictures are not of productions, but theatres. The cosy musk of a cigar smoked earlier that morning hangs in the air. According to the biography, he sits on a needlepoint cushion that bears Mark Twain's comment on death and smoking: "If I Cannot Smoke Cigars in Heaven Then I Shall Not Go."
"I think producers today are very brave," he says, with that trademark measured tone that has closed deals for nearly 200 plays and one movie, John Cleese's Clockwise.
"The writers that I used to produce were very keen on the West End, Now they're not." These days they prefer to go to the subsidised theatre, where there is more room for experimentation, and more time for rehearsal.
The list of writers that Codron has produced is a roll call of the best British dramatists - Tom Stoppard, Michael Frayn, Joe Orton, Alan Ayckbourn, Simon Gray, Alan Bennett
and David Hare. More recently, Patrick Marber, Joe Penhall and Moira Buffini.
But perhaps he is most famous for the risk he took, 52 years ago, on a then virtually unknown playwright called Harold Pinter, who had a play called The Birthday Party. Codron has said that it was his Jewishness that helped him recognise the play's and Pinter's worth.
"I knew that this was a new and menacing voice," he says in his book. "I think because of the menace and the fear, but also maybe because of our mutual Jewishness… some of the writing, a lot of the character Goldberg's incantatory speech, spoke very strongly to me."
It did not speak strongly to the critics. Codron took the play to Oxford, Cambridge and, of all places, Wolverhampton before bringing it to London. What happened there has gone down in theatre history. The critics almost all gave the play a resounding thumbs down. All except Harold Hobson, who was the only London critic to agree with Codron's instincts. It might have been enough to save the run had Hobson been able to make the first night at the Lyric Hammersmith where the play had its London premiere in 1958. But Hobson's review came out late - too late to save the production - and the play closed after a week.
"I was relying very heavily on Harold Hobson," remembers Codron. "He liked The Room [Pinter's first play]. But tragically he didn't make the first night. I saw him subsequently many times, but I never did find out why."
"But even if he had, we don't know how long we would have survived anyway. All the Sunday notices were poor."
As Codron's career progressed not all critics of his productions were of the type who work for the media. There were his parents too. Haco and Lily used to watch many of their son's out-of-town try-outs in Brighton, a place notorious for unforgiving audiences. "They became part of the dreaded Brighton opinion that we all used to worry about," says Codron. "They would go every week to see a play at the Theatre Royal and ring me the following day with their views. My father always thought the plays were too far-fetched."
A production of the 18th-century comedy, The Clandestine Marriage, however, caused more confusion than criticism. "For some reason they went to the theatre thinking it was called 'The Candelstein Marriage'," chuckles Codron. "They couldn't understand where it had all gone wrong."
As for the paid critics, Codron bears no grudges, which is perhaps no surprise considering that he has received many more good notices than bad. "I wouldn't be here without critics. And I think we have good critics at the moment - apart from one or two strange appointments," he says enigmatically.
Nor are there grudges for the occasional playwright who jumped ship to another producer. Codron was the first to take Patrick Marber into the West End, with his play Dealer's Choice. But Marber moved on for the even more successful Closer. In Putting It On, Codron says that he understood that Marber might have been after a younger producer with a higher Broadway profile.
It all adds to the calm, even philosophical air of a man whose modus operandi has been to stroke more feathers than he ruffles. The lifetime achievement award he was given at the latest Laurence Olivier Awards ceremony - an event organised by fellow producers - was universally welcomed. One critic said recently it was about time Codron was knighted.
"What an ordeal. I've never been an admirer of the Oliviers," he says. "They go one forever. And anyway, I only got it because it's a 'My God, is he still here?' award."
But he is wrong. The citation for a previous award he received in 2006, marking his 50th year as producer, put it another way. It was in the form of a poster with words specially written by the dramatist Michael Frayn. It says: "Michael Codron, Prince of Producers, Emperor of Impresarios, King of Comedy, Dreamer of Drama, Employer of Players, Author of Angels, Angel of Authors, Foremost of Friends."
The Olivier was, I say, not a "My God is he still here Award", but a "Look what he has achieved award".
"Perhaps", says Michael Codron.