Revealing mistake: A couple cross the road to enter Victoria Coach Station, London. There is the noise of a coach braking hard and they throw themselves away from a coach just inside the entrance, which obviously was not moving at the time. They walk into the station and talk to an inspector, while the same coach is driven out of the entrance past where it is supposedly parked.
Revealing mistake: During the interrogation after the Albert Hall assassination attempt, the telephone used is an obvious Western Electric American-made phone instead of a British-manufactured telephone, betraying the fact that the interiors for the movie were shot in Hollywood.