Mrs Norris refers to the Yorkshire Ripper as an example of police incompetence. The Yorkshire Ripper, Peter William Sutcliffe, killed 13 women over a five-year period between 1975-80, mainly in the West Yorkshire area. During the manhunt, Sutcliffe was questioned nine times and released during the course of the investigation.
The same basic storyline was used for the film Dangerous Davies: The Last Detective (1981) starring Bernard Cribbins.