The date in which the most sophisticated and deadly spy network in the world advised the President of the United States to step outside all legal channels to preserve the security of the country was October 15, 1972. The date in which they thought they may have made an incredible mistake was September 15, 1973.
This was Dirk Bogarde's first film for two years after taking a hiatus following the mentally and physically exhausting filming of Death In Venice (1971). Bogarde broke his lifetime rule of not accepting films where he wouldn't be top billed and took this role because he wanted to work with Henry Fonda who was one of his acting idols. Bogarde noticed on the set that Fonda didn't carry the full script around with him. He only had the pages that his character was in.
According to "Film Review 1974-1975", this movie was "based on the famous Philby spy case (and was) a parallel to the famous Philby spy case."
The opening prologue states: "That which enables a wise ruler and a good general to strike, to conquer and to attain goals beyond the reach of ordinary mortals is "Prior Knowledge" SUN TSU (fifth century B.C.). Some versions of this movie feature the following title card addenda to this movie's prologue: "In the modern world, this 'prior knowledge' is synonymous with 'Secret Services'. Novelists call it...'Espionage'."
In addition to the parallels between MI6's Philip Boyle (Sir Dirk Bogarde) in this movie and Kim Philby in real-life, there is another parallel between the head of the C.I.A. characters. The name of the Director of the C.I.A. in this movie, Allan Davies (Henry Fonda), seems to be a tribute to Allen Dulles, who, in real-life, was the Director of the C.I.A. from 1953 to 1961. Beside their names, the resemblance of facial lines of these two men is remarkable as well.