This is the third episode of "Endeavour" to be directed by the show's leading man, Shaun Evans. He has now directed more episodes of the show than anyone else.
The poem which Dorothea Frazil quotes to Morse ("The old order changeth...") is "Morte D'Arthur" by Alfred, Lord Tennyson.
There are several mentions in the story of the "Angry Brigade", a group of far-left agitators who were responsible for about 25 explosions in various parts of Britain between 1970 and 1972. The explosions targeted buildings and objects, but (as is mentioned in the dialogue) not people; however, one man was slightly injured. Of the eight Angry Brigade members who stood trial for terrorist offenses, four were acquitted. One of the ringleaders famously remarked that most of the (few) members of the group should have called themselves "the Slightly Cross Brigade", not "angry".
Surprisingly, there are hardly any overt references to the events of the previous story, "Zenana". Some way into this new story, Thursday refers obliquely to "what happened last year", in particular to the death of Mrs. Bright (though he does not specify the event). The unsolved aspects of the towpath murders and Morse's problems with the Italian police rate no mention. It is clear, however, that Morse has been badly affected; he is now drinking more heavily than ever and is late arriving to collect Thursday because of a hangover; he is also still smoking, a new vice for him. He is even seen drinking alcohol (out of a bottle) during his working day, something Joan Thursday comments on - she clearly believes he is turning into an alcoholic. Jim Strange's knife wound, received at the climax of "Zenana", has kept him off work until the beginning of this case (that is, for about two months); he is noticeably thinner than ever before.
Unlike earlier depictions of real-life people in "Endeavour" stories - Princess Margaret in "Rocket" or Sally Alexander in "Oracle" - Eamonn Andrews is not shown only fleetingly and without speaking. The actor playing him is voice-over artiste and "Spitting Image" impersonator Lewis Macleod, who has quite a lot of dialogue and some minutes of screen time. He both looks and sounds uncannily like the real man, and is even more or less the age Andrews would have been in 1971.