Based on the book that marks the debut of Miss Marple.
Mrs Protheroe (Polly Adams) is seen reading the book The Broken Road by A E W Mason. Mason was the creator of Inspector Hanaud who inspired Agatha Christie to invent Hercule Poirot
The prescription on the bedside table of Christopher Hawes is from Mr. Badger, the chemist. This is the same Mr. Badger Miss Marple discusses in 'The Body in the Library'.
Cheryl Campbell (Griselda Clement) and Ian Brimble (Sgt. Lake) were both in Inspector Morse series 4 episode 1 The Infernal Serpent
Three performers (Paul Eddington, Norma West and Rosalie Crutchley) all appeared in The Prisoner.