Factual error: A uniformed constable addresses Detective Sergeant Ripley as "Guv" in this episode and another officer addresses him as "Sir" in the following episode. These terms of address are reserved for officers of the rank of Inspector or above. Sergeants are addressed as "Sarge", "Skipper" or "Skip."
Factual error: The detectives determine that the killer must be using a boat which he used to dump the first body next to a canal in Birmingham. However, the barge he is using is far too large to navigate the Grand Union Canal from London to Birmingham, let alone the canals within Birmingham itself.