Character mistake: In a shot that flashes by very briefly, a London newspaper's headline is shown: "Sherlock Holmes Aides Police." "Aides" should be "aids".
Character mistake: In the scene showing the outside of the hotel the British flag is flying upside down. The wider white band on the white X has to be top left next to the top of the flag pole. It is at the bottom, which is a universal distress sign.
Answer: The gun was modified to where it would not fire a bullet. It remained in the barrel.
MasterOfAll