For some unknown reason, the voice of Anne Wadkin (actress Jeanne Roland) was dubbed by another actress. The character Ms Roland plays in this episode is supposed to be Asian (specifically Chinese) Ms Roland - though born in Burma - was not of Asian descent, and she spoke with a soft French accent
Peter Madden also appeared in the series, Secret Agent (1964), as Hobbs, John Drake's superior, in several episodes. Subsequently, he appeared in the opening sequence of the follow-up series, The Prisoner (1967), as the undertaker, who gasses the man unconscious.