Robert Vaughn says in his memoirs that Jason Robards, Jr. was very unhappy during the filming period, and dubious about the end result.
Despite his "also starring" billing, Christopher Lee worked on the film for only a day and has only five lines. He said that the only direction that he received from Stuart Burge was, "You realise, of course, that Artemidorus is quite, quite mad."
A topless woman (who somehow was missed by censors) walks past in the background during the opening credits sequence.