When Lewis and Hathaway discuss possible ways of manipulating someone to commit a murder, Hathaway quotes Henry II: "Will no one rid me of this turbulent priest?" Allegedly said to move knights to murder Thomas Becket.
Lewis finds Temazepam and Finadrine in the victim's medicine cabinet. The one helps with insomnia, the other with energy, at least when it's spelled Phenadrine. Quite the push pull combo. Dr. Hobson reports the stomach contents as "Caffeine, nicotine, alcohol, amphetamines". Professor Hawes was living dangerously as alcohol can be fatal when mixed with Temazepam.
The Vauxhall cars of previous series have been replaced by a BMW.
The two students who are candidates for the Wednesday Club--Mia Wallace and Vincent Vega--"borrowed" their names from two main characters in the movie Pulp Fiction.
Alex Jennings appeared in The Sins of the Fathers (1990) as Victor Preece. Richard Durden appeared in The Dead of Jericho (1987), the first episode of Morse and Quartet (2018).