Clive Revill was fourth choice and the part was not cast until shooting had begun.
Peter O'Donnell complains that of his original screenplay, only one line remains: "What do you know about Wilberforce?" However, he accepted the invitation to write a novelization of this film. The book, based upon O'Donnell's original screenplay rather than this film, was a huge success and spawned a series of best-selling novels until 1996.
Many scenes set in London did not make it to the final print. Among those performers featured in these deleted scenes was Maureen Pryor.
Modesty Blaise is introduced with a close-up of her legs in fishnet stockings, sitting on a couch by two magazines, one showing a color photo of actress Monica Vitti, and on top a full page copy of the Modesty Blaise comic strip where she is depicted as a huntress with a bow-and-arrow and a revolver. Willie Garvin is introduced looking at a blow-up of the same scene, in a wall frame.
When Modesty rings the doorbell an an apartment building, the second name down on the address sign next to the door bell says in mock "Dutch": Van Dijk.
When the shorter red haired assassin puts out a cigarette in an ashtray, the "Dutch" logo on the ashtray spells: Fokking.