Which long-running play, based on a book by Agatha Christie, has been performed in a London theatre for over 68 years?

The play that has been performed in a London theatre for over 68 years, based on Agatha Christie's work, is indeed "The Mousetrap." This iconic production first premiered in 1952 and has since become a significant part of London's theatre scene, largely due to its status as the longest-running theatrical production in the world. The play is a classic murder mystery that engages audiences with its intricate plot and surprise twist ending, hallmarks of Christie's writing style.

Given its exceptional longevity and popularity, "The Mousetrap" has maintained a unique place in theatrical history, attracting both tourists and locals who are eager to experience this quintessentially British performance. Other works by Agatha Christie, such as “Death on the Nile,” “And Then There Were None,” and “Spider's Web,” are also notable but do not share the same length of ongoing performance in London theatres.