Marcello Mastroianni's first film role in English. He learned his lines phonetically and was much praised by director John Boorman as being one of the most patient and co-operative of all actors; he was also popular with the other actors and crew.
Although long married, Marcello Mastroianni was having a rather well-publicized affair with Catherine Deneuve at the time this film was made. Director John Boorman recounted (in a warm, loving tribute to the actor after his death) that the one thing Mastroianni would insist on every day was that he would work no later than 5 p.m. At this time, Deneuve would appear on the studio floor to take him in a chauffeur-driven limousine to one of the grandest of London hotels, but, instead of going off with her, Mastroianni would go straight to a nearby telephone and put in a transcontinental call to his wife in Rome. These calls, always extremely affectionate, would never last less than an hour and would often go on far longer. Deneuve would fume silently in the corner throughout, and, when he had finally finished, would hurry him out through the sound-stage door. As he left, Mastroianni would turn to Boorman and the remaining crew members and, with a slightly forlorn, world-weary expression on his face, the sort of look he had worn in so many films, he would shrug slowly. Then the doors would close behind him, said Boorman, "and we'd all feel very sorry for him."
Billie Whitelaw appears topless in this film.