The famous sex scene between Donald Sutherland and Julie Christie was a last minute on-set idea from director Nicolas Roeg who felt that otherwise the film would have too many scenes of the couple arguing. Most of the scenes around it are improvised.
Renato Scarpa who plays inspector Longhi didn't speak any English. He just read the lines he'd been given without knowing what they meant, which added to the sinister quality of his character.
Writer Allan Scott was pleased to see a bottle of The Macallan (of which company he was the deputy chairman) beside the bed in the big sex scene.
Donald Sutherland and Julie Christie met for the first time on the set of this film. The first scene they had to shoot was the sex scene, as Roeg wanted to "get it out of the way" and then move on to the "bone" of the matter. Christie was terrified.
Clips from this film (along with others directed by Nicolas Roeg) appear in Big Audio Dynamite's 'E=MC2' video (1986).
In order to avoid an X-certificate rating for the film's American release, 9 frames (less than half a second) had to be cut from the intimate love sequence between Donald Sutherland and Julie Christie.