Alasdair Buchan, who directed his version aged 11 in 1997, will play mysterious stranger in long-running whodunnit

As the curtain falls on every performance of The Mousetrap, the world’s longest-running play, applauding audience members are famously urged not to go on to reveal the secret solution to the murder mystery.

This autumn, however, a fresh element of intrigue has been added to the plot of Agatha Christie’s enduring hit, which first opened in 1952 at Nottingham’s Theatre Royal.