Because the stars were all too old for their characters, the movie was nicknamed "Elderly Gang Goes Off to War" by the British press.
Despite the narrated prologue (see Memorable Quotes) setting the "historical background", this is a work of fiction. There was no such mission, because there never were any guns of Navarone.
Director J. Lee Thompson's first American feature was also his opportunity of working with some of the biggest Hollywood stars.
During WWII, 'David Niven' commanded units in both the Commandos and the GHQ Liaison Regiment, a special reconnaissance unit that operated behind enemy lines.
For the scene where the commandos scale the near-vertical cliff, the rockface was a painted backdrop laid out on the ground, so the actors were actually climbing over the studio floor and then the image was tilted in camera.
One of the Rhodian locations used in the film has been renamed "Anthony Quinn Bay" after the actor was reported to have bought property nearby.
Original director was Alexander Mackendrick, but he was fired by Carl Foreman due to "creative differences".
Producer Carl Foreman brokered a deal with the Greek army where he had 12 destroyers and over 1000 infantrymen at his disposal.
Some members of the Greek royal family and their entourage were extras in the café scene as they were visiting the set on the day that scene was being filmed.
The $50,000 fee paid to composer Dimitri Tiomkin was the highest fee paid to a composer for a single feature film score up to that time.
The only time David Niven ever smoked cigarettes on screen.
The original 1961 road show release used Technicolor prints made in London, which gave the film eye-popping clarity and disguised many of the imperfections of the sets and special effects. When it came time to turn out mass runs of prints for the general release, Columbia shipped the original negative to a bargain-rate lab in New York, where it was reconfigured for normal Eastmancolor printing. This meant re-cutting the negative to insert standard opticals to approximate the Technicolor process's smooth dissolves, etc. No preservation separations were made and the negative wasn't properly protected. Poor-quality dupe sections were soon patched in to replace damaged pieces of the negative. Eventually two entire reels would have to be replaced in this way, after that New York lab accidentally destroyed the originals through handling errors. Columbia also discarded the film's original sound elements and stereo tracks. A collector's magnetic print was used to recover the original four channel stereo mix.
The plot went through so many twists that Gregory Peck finally submitted his own version to Carl Foreman: "David Niven really loves Anthony Quayle and Gregory Peck loves Anthony Quinn. Tony Quayle breaks a leg and is sent off to hospital. Tony Quinn falls in love with Irene Papas, and Niven and Peck catch each other on the rebound and live happily ever after."
The screenplay differs drastically from Alistair MacLean's book in terms of characters, including the identity of the traitor and the two women who don't even appear in the novel.
The top grossing film of 1961.
There had been some concern that the cast would not get along, particularly since Anthony Quinn had a reputation for being difficult to work with. However, in the event things went smoothly, although according to Quinn Stanley Baker did not get along with the others. Some of the cast believed that Baker felt he should have been playing Mallory.
There is no Navarone in real life.
There was reportedly much tension between many of the stars (particularly Gregory Peck and Anthony Quinn) early in the film's production, but the cast gradually bonded over endless games of chess.
There was some surprise that Stanley Baker, who in 1960 was considered the most popular British movie star, accepted the relatively small supporting role of Private "Butcher" Brown. Baker revealed that he wanted to be in the movie because he was impressed at how anti-war the screenplay by the blacklisted writer Carl Foreman was.
When Mallory says of Stavros: "He's from Crete; those people don't make idle threats", he's inverting the famous quote by the Cretan philosopher Epimenides, that "all Cretans are liars". The end of the movie reveals which of the two is right.