The book has many characters, but the Stephen Joseph Theatre had few actors. It was this constraint, irksome at first, that led me to find the structure that became the central strength of the show. Once I'd found it the writing became a happy process, and the rehearsals, too, were positive and creative with Robin and the actors Jon Strickland, Dominic Letts and Lesley Meade.

Fourteen years on, and the script really hasn't changed much. There have been countless productions all over the world - some wonderful, some laughable - but I feel very lucky that Robin Herford has directed every new cast in the West End, where the quality's stayed consistently high, and the show continues to terrify.