Corrected entry: In the scene where Olivier fires the miniature cannon at the dart board, you see someone walking passed the window going over to the front door and looking through the letterbox.
Corrected entry: Shooting someone in the head with a blank (as Andrew does) whether it's at point-blank range or from twelve inches, would likely kill or at the very least cause serious injury to the victim.
Correction: It depends entirely upon the load. Be aware that what you are seeing on the screen is what really happened - a blank was fired close to an actor's head - so there is obviously a safe way of doing it.
Correction: I have seen this movie many, many times and unless there is more than one version, I cannot recall any scene where a cannon is fired at the dartboard.