This episode's clothing for Ms Moira Lister were by Mnsr Christian Dior - only one of two episodes to utilise a fashion courtier so well-known at the time. This was done, as her character - Claudia Jordon - was a stylish woman of wealth and taste, living in France (the other episode was outfitting Ms Wendy Craig, in I Can Only Offer You Sherry, as she was a friend of the designer).
Patrick McGoohan, who was a method actor, met his match in Denholm Elliott, who also wanted to practise for hours before filming their race.