Who is the killer in The Mousetrap?

Having actually seen a production of Agatha Christie's murder mystery The Mousetrap, I am violating an informal pledge to not divulge the murderer's identity. Christie's play has been performed continuously for 64 years, and at the end of each performance, in London's West End, the audience is asked by the cast to keep confidential the murderer's identity. That said, the murderer is revealed as Sergeant Trotter, an idiosyncratic late-comer to the quintessential Agatha Christie setting, an isolated retreat at which is assembled the pool of suspects. Trotter's appearance at the snowbound inn that provides the play's solitary setting is unsettling, as he does act sufficiently peculiar so as to invite suspicion -- a not unremarkable reaction given the nature of the story. The "who-dunnit" nature of Christie's work, however, is intended to keep audiences guessing, and suspicion is deliberately directed toward the interestingly-named "Christopher Wren," an architect whose peculiar mannerisms exceeds even those of the individual calling himself "Sergeant Trotter." That English history does, in fact, include a famed 17th century architect named Christopher Wren does serve to direct suspicion towards this character, but, as noted, Trotter's behavior seemed a bit unsettling, and it was no surprise when he turned out to be the murderer whose real name was Georgie and that he was at the center of the chain of events, as a child, that has brought this particular group of individuals together.