Following the success of their version of Why Didn't They Ask Evans? (1980), the same production team reunited for this Agatha Christie adaptation, including Pat Sandys, Tony Wharmby and Jack Williams. Both productions also included the actors: John Gielgud, James Warwick, and Robert Longden.
John Gielgud was mentioned by name in Agatha Christie's 1976 novel "Sleeping Murder". This is his third of four appearances in an Agatha Christie adaptation. The others being: Le crime de l'Orient-Express (1974), Why Didn't They Ask Evans? (1980), and Rendez-vous avec la mort (1988).
The meeting is said to take place at Wyvern Hall. At 1:18, the clock on top of the building is shown striking 3:00am and in the foreground you can see an architectural ornament of a wyvern (a dragon with two legs and two wings), presumably associated with the name of the estate.