Continuity mistake: In the scene where Gerald Tetley confronts Major Tetley (his father)and talks about how his father gave the order for three innocent men to be hanged. His father listens till Gerald finishes then walks to a door feeling guilty, opens it and goes inside the room. The shot is focused on the door. A shot rings out and the Major has killed himself. Meanwhile we still see the door, then it opens and within a second the shot goes back to Gerald. (01:10:10)keiko
Continuity mistake: When John Mills is looking through the periscope whilst searching for the German battleship the side view shows him moving the periscope from right to left, but when it suddenly cuts to a shot of what he is actually seeing through it the periscope is strangely moving from left to right.
Revealing mistake: Towards the end when the Phantom's lair is collapsing, you can see bricks falling into the sewer water and floating. Obviously they were made out of light-weight material and not out of actual stone.
Continuity mistake: In the scene where the tank crew meet up with the weary band of soldiers, Fred Clarkson (Lloyd Bridges) has a very distinctive graze on the right side of his forehead. It seems to disappear then appear then disappear during the film. When Clarkson lies injured there is no sign of the graze - there should at least be a small mark of the graze but there is nothing.