Early into filming, they became lovers, and as Hyler and other remembered, “they were together most evenings after shooting.” At the same time, Audrey relocated from her first residence, an apartment hotel at 3435 Wilshire Boulevard (near Paramount Studios), to a two-room furnished rental at 10368 Wilshire (closer to Holden’s residence), where their rendezvous were conducted. In those days of the “morals clause” in Hollywood contracts - a paragraph that could destroy a career if public decency was offended by an actor’s private life - Audrey and Bill had to be extraordinarily discreet. In this case, the matter was compounded by the fact that he was married and a father. Of Mel, Audrey was uncertain; in any case, no promises had been exchanged, and he was away at work. Playful, romantic and attentive, Bill was, for the time being, irresistible.
(…) Holden’s life was ordinarily complaisant - until Audrey. In late October , he brought her home for dinner (a curiously repeated pattern in the marriage), and Brenda at once picked up the scent of a real threat. Later, she demanded that he end the liaison, but the lovers simply continued the affair at her apartment and sometimes, more injudiciously, in their studio dressing rooms. “Audrey embodied everything that he admired in a woman”, according to Holden’s biographer, Bob Thomas. “She was young - eleven years younger than himself. Audrey considered him the handsomest man she had ever known, and she was entranced by his manly charm and gentle humor”..
(…) She was completely won over when he promised to divorce Brenda and marry her. In a delirium of happiness that made their onscreen love scenes eminently credible, Audrey at once raised the issue of children: she wanted two, three, four and more - she would abandon her career to have a family. For a few weeks, until their last scenes together, Holden temporized, and then broke the news of his sterility. On the spot, Audrey ended the affair. “I really fell in love with Audrey Hepburn,” Holden said later, “but she wouldn’t marry me. So I set out around the world with the idea of screwing a woman in every country I visited.” Years later, Audrey’s reaction to his tale of international intrigue consisted of two words only: “Oh, Bill!”