The production was difficult for John Wayne, since he was suffering from recently diagnosed heart problems, and had just recovered from a severe bout of pneumonia.
This movie proved to be one of John Wayne's least successful movies at the box-office. Wayne said he would not have made this movie if he had known McQ (1974) was only going to be a moderate success.
This movie contains a unique piece of footage of the inside of the Garrick Club (known as the actors' club) which traditionally does not allow cameras, and only agreed to let this movie in because Sir Richard Attenborough was a long-term member. In the scene in which Brannigan and Commander Swann are at the bar in the Garrick Club, on the wall behind them are portraits of Sir Laurence Olivier and Sir John Gielgud, both in Garrick Club ties.
Brian Glover was a well-known wrestler. He said in interviews that his fight scene was the only fight he was paid to lose in his career.
During his stay in London, John Wayne met Katharine Hepburn for the first time. Also in London for a film shoot, Love Among the Ruins (1975) with Sir Laurence Olivier, Hepburn made a point of introducing herself to Wayne, a man she admired greatly despite their obvious political differences. The meeting led to their only movie pairing, in Rooster Cogburn (1975).