The mystery disease that Arthur claimed Terry was suffering from was originally scripted as the very rare but real affliction of Huntingdon's Chorea. However, after complaints from viewers, this was changed to the fictional 'Spotter Syndrome'. You can see the edit was dubbed on post production as we only hear Arthur say it off screen.
Jan Francis (Sarah Bates) later appeared alongside Dennis Waterman in 16 episodes of Stay Lucky (1989) from 1989-1991. She also later appeared with Dennis Waterman and George Cole in Powerhouse (2007)
Benjamin Whitrow (Doctor) previously appeared with Dennis Waterman in The Sweeney (1975). He played Detective Chief Superintendent Braithwaite in four episodes of Season 4. He also later appeared with him in London Underground (2014)
Timothy Carlton (Granger) later appeared in An Officer and a Car Salesman (1988) as Assistant Commisioner. He previously appeared with Dennis Waterman in Cover Story (1975). And he later appeared with him in The Howling (1989) and Fool's Gold (1989)
Melanie Hughes (Shop Assistant) previously appeared with George Cole in A Safe Place (1985) and Cards on the Table (1985)