Finding The Mousetrap to be conventional and often uninspired, Shorter assesses the play's lengthy theatrical run.

Once upon a time (and a very good time it was) the Abbey's Lady Gregory said: 'We went on giving what we thought good until it became popular'. No better motto could be found for theatrical managers, but how many heed it? The motto now is to give what the manager thinks will be popular until it is generally thought good. Hence The Mousetrap. It must be good because it has run for so long.

Agatha Christie's thriller has now been on for 21 years. It has broken every conceivable theatrical record. It has made its manager's West End reputation. It has been visited by successive generations of playgoers. It has caused annual celebrations to be held. It has seen the coming and going of over 150 actors and actresses. It has become...