The Mousetrap was initially performed as a radio play in 1952 and was broadcast by the BBC with the title Three Blind Mice. The radio play had been commissioned in 1947 by Queen Mary, who was a Christie fan. The forty-five minute play was based on a short story on which Christie had been working; however, audience reaction was so positive that Christie went back to work on the script, elaborating on it, and with its first performance on October 6, 1952, The Mousetrap became a stage play. After a seven-week tour, the play opened in London at The Ambassadors Theatre on November 25, 1952. The play later transferred to St. Martin's Theatre in London on March 23, 1974 and has been running there ever since. The Mousetrap has broken several records for its continuous theatrical run since its opening, and it is estimated that more than four million people had seen the play by the time its twenty-five year anniversary was celebrated in 1977. After another twenty years of performances it is safe to speculate that an additional three to four million people have probably sat in the dark and tried to puzzle out the identity of the murderer. Performances of The Mousetrap continue to benefit from tourists who seek out the play both for its artistic merits and for the joy of being part of a theatrical tradition. Christie signed over the royalties from the play to her grandson at its opening in 1952. It is thought that he has become a multimillionaire from the royalties of this one property alone.