Rebecca Saire, who plays Hazel Radowicz in the story, is in real life the wife of Roger Allam, who plays Chief Inspector Thursday.
At the end of an earlier episode, "Coda", when Fred Thursday bids farewell to his son Sam as the latter departs for the army, his last word of advice is, "Don't volunteer for anything!" In this episode, set a year later and the only subsequent one in which Sam Thursday has appeared, the very first thing he does is volunteer for something.
The poem recited by Lt.-Col. McDuff at the departure ceremony is "Vitaï Lampada" by Sir Henry Newbolt.
The real name of the fascistic Lady Bayswater is said to be "Charity Mudford", which can hardly fail to remind viewers of the real-life Unity Mitford. She was the daughter of Lord Redesdale, and is reputed to have fallen in love with Adolf Hitler in the early 1930s and even to have harbored hopes of marrying him. However, the character is, as played by Caroline Goodall, much more like Unity's sister Diana, who was the second wife of the notorious Sir Oswald Mosley, the founder of the British Union of Fascists. Sir Oswald openly supported Hitler and Mussolini in the 1930s and was, with his wife, interned throughout the Second World War. He was, however, still alive in 1968, the year in which this "Endeavour" story takes place, whereas Lady Bayswater's husband is said to be long dead.
This episode marks the first time in the entire five-year run of the series thus far that Endeavour Morse is seen smoking. Nor was the character ever seen smoking in the later-set "Inspector Morse" series, where he was several times specifically said to be a non-smoker.