A fervent Catholic, The Prisoner star took exception to O'Neill's personal life and didn't hold back in letting her know.
Director David Cronenberg recalls, "He had extreme Catholic views about sexuality, which came onto the set.
"My leading lady... came to me incredibly distraught and said, 'Patrick said, 'Are you a whore? Are you a slut?' And he started to lay into her because she'd had, like, five husbands.
"That was Patrick, and those were the things I had to deal with as a relatively young director. He was probably the most difficult actor I ever worked with, though he gave a fantastic performance."
At the time, O'Neill had wed three times. She went on to marry another two men and has been wed to Mervin Louque since 1997.