The film that Cust watches in Doncaster is Alfred Hitchcock's 1932 film Number 17 (1932). His wife, Alma Reville, was one of the scenario writers.
It is revealed that Captain Hasting's initials are "A.J.M.H."
The first film viewed by Cust with great fascination is Footsteps in the Sand (1939) starring Raymond Massey.
The first of two episodes to feature Nicholas Farrell. Here he plays Donald Fraser, thirteen years later he played Knighton in The Mystery of the Blue Train (2005).
The action music from the contemporary film showing at the cinema in Doncaster is also featured in Monty Python and the Holy Grail (1975), for the scene where Sir Robin encounters the three-headed knight. The piece is 'Desperate Moment' by Kenneth Essex.