Continuity mistake: After the first murder in the nightclub when Durkin and the other policeman are on the boat, talking about Stone, their position on the river keeps changing. In some shots they have passed Parliament and Westminster bridge and in others they are still approaching them.
Factual error: The radio at the beginning of film says that the flood problem will increase with the approaching full moon. Later it is revealed that the killer only kills when there is a new moon. Since he kills that evening, and tides are highest with full and new moons, the radio should have been warning about that evening's tide, not the high tide in 2 weeks time.