The St. Martin’s Theatre opened on 23 November 1916. It was designed as part of a pair alongside the Ambassador’s Theatre. The Ambassador’s opened in 1913, and World War 1 delayed work on the St. Martin’s for 3 years. The inaugural production was the musical comedy Houp La! Other notable productions include R.U.R., The Grass is Greener, The Wrong Side of the Park, and Sleuth. In 1974, The Mousetrap, which had been running at the Ambassador’s since 1952, transferred into the St. Martin’s. The production is still running to this day, Celebrating its 60th year in the West End in 2012 (as well as its 25,000 performance) and cementing its position as the longest running theatrical production in the world.