Hammer president Michael Carreras replaced original director Monte Hellman, receiving sole credit on screen.
Monte Hellman worked for three weeks on the film as director. He shot all of the scenes involving Peter Cushing and Anton Diffring and very few of the fight sequences.
Three directors of photography are listed during the opening credits. John Wilcox was the original cinematographer. When he became ill, suffering from liver problems, his assistant Roy Ford took over, and when Michael Carreras took over as director, Brian Probyn became the DOP.