The names of crew members Pauline Harlow (script supervisor) and Steve Fish (sound maintenance) appear on the white board of the undertaker as the names of corpses to be cremated.
The title of this episode, "The Ramblin' Boy," refers to the 1964 Tom Paxton song. The father and son are singing the song in the opening scene. And--near the end of the episode--the son, sitting on a bench, is listening to it over his headphones as Lewis approaches him
So here's to you my ramblin' boy/ May all your rambles bring you joy/ So here's to you my ramblin' boy/ May all your rambles bring you joy... ...He left me here to ramble on/ My ramblin' pal is dead and gone/ If when we die we go somewhere/ I'll bet you a dollar he's ramblin' there.... -- Tom Paxton
This episode happens to feature Taron Egerton, speaking and singing with his actual Welsh accent, when he was a relatively unknown actor, in a relatively minor role, hence his name isn't in the opening title credits. He would later become very well known for playing Eggsy in the Kingsman film series, and Elton John in the biopic Rocketman.
Peter Davison is also known as the 5th Doctor, in the Doctor Who franchise and Father-in-law to David Tennant, the 10th Doctor. David Tennant co-starred in Doctor Who with Billie Piper, and attended her wedding to Laurence Fox, DS James Hathaway. Note: the couple has since split.