The mention of the fruit "medlars" and the process of letting them rot before creating the jelly is accurate. Medlars in their "fresh" state are basically inedible, the fruit being hard and acidic. The rotting process, known as "bletting", renders them edible and allows them to be used in jellies and cooking. The same characteristics and processing are found in quince and persimmon.
The silver convertible sports car owned by Adam is an Aston Martin DB6 Volante from the 1960s.
Actor Adrian Rawlins, who plays Adam Kayne in this episode, would later garner tremendous international fame as James Potter, the father of Harry Potter, in the epic, 8 film series, that chronicles the adventures of Harry in the wizarding world, based on J.K. Rowling series of novels. Ironically, the first film begins with the death of his character, as well as of Harry's mother, Lilly, setting off a course of events that would become legend within the world of the books/movies, and in the real world as well.
Benjamin Whitrow plays Hugo Balcombe in this episode. He returns in episode 12.3, Secrets and Spies (2009), in the role of Sir Malcolm Frazer.
Ellie Haddington plays Joan Farley in this episode. She returns in episode 20.2, Death of the Small Coppers (2018), in the role of Ginny Welton.