As Rudolf Hess, 77-year-old Sir Laurence Olivier was in poor health during filming, and required a nurse to accompany him during production. Olivier was also beginning to suffer with memory problems, and labored for hours on his one long speech, because of having trouble remembering the dialogue.
Originally, this movie was supposed to star Richard Burton and Sir Roger Moore. However, Moore did not like the script, and after Burton's death, he decided to pull out.
According to Donald Spoto's "Laurence Olivier: A Biography" (1991), Rudolph Hess' son Wolfgang Rüdiger Hess (a.k.a. Wolf Rudiger Hess) thought that the likeness of Sir Laurence Olivier compared to his father was "uncannily accurate".
After Richard Burton died, producer Euan Lloyd had to re-cast his part. Lloyd contacted Edward Fox, who was in the country working on his house. Fox agreed to do the movie, so he could add another wing onto his house.
Richard Burton was set to play his character from "The Wild Geese (1978)," Allen Faulkner, but died a few days before filming began. Edward Fox stepped in to play Alex Faulkner, the brother of the character played by Burton.