The elderly Peter, Marquis of Ross, is played by Peter Penry-Jones. His son Laurence Penry-Jones plays the marquis as a young man, forty years earlier in flashback.
This is the last credited film role of Ursula Howell, who plays Lady Isabel.
Nigel Harrison plays Dave Ripert in this episode. He returns in episode 10.8, Death in a Chocolate Box (2007), in the role of Eddie Marston.
Merelina Kendall plays Miss Alice Leonard in this episode. She returns in episode 17.2, Murder by Magic (2015), in the role of Dr. Dorthea Grenville.