The collapse of Cranmer House is clearly suggested by the real-life tragedy of Ronan Point, a London tower-block in the Canning Town district. It partially collapsed in May 1968, about 18 months before the events in this "Endeavour" story take place. Four people died and another 17 were injured in the collapse. As with Cranmer House, the Ronan Point collapse was initially ascribed to a gas explosion, but its chief cause was later found to be alarming structural deficiencies. As a result of the Ronan Point tragedy, laws were changed and made more stringent.
A "degüello" is a Mexican bugle call, used to signify to fighting troops that no quarter is to be given to the enemy. The word can also mean "decapitation".
The (uncredited) narrator of the newsreel about Cranmer House shown at the beginning of the episode is, in fact, Roger Allam, the actor who plays DI Thursday.
DI Thursday, warning Morse, speaks darkly about his investigations leading to "another Blenheim Vale", upon which he does not elaborate. "Blenheim Vale" was the name of the former children's home featured in the famous "Neverland" episode which closed Season Two of "Endeavour", a story which left Thursday in hospital with a bullet in his lung and Morse in jail accused of murder.
In interviewing Nicholson, Thursday expresses his taste in books by saying, "I'm a Holly Martins man." Holly Martins is a fictional character in the movie "The Third Man," a movie based on a story by Graham Greene and directed by Carol Reed. The character Holly Martins (portrayed by Joseph Cotten) is a pulp Western fiction writer who in turn idolizes Western writer Zane Grey.