When the man running the pub in the village where the film was being shot discovered that he had used up his alcohol ration on the film crew, he was so distraught he committed suicide.
The church in the film is the church in the Buckinghamshire village of Turville, and is named St Mary Virgin Church.
The poem from which the title is taken, and which appears at the start of the film, is actually the second of four epitaphs written in 1918 by Greek scholar John Maxwell Edmonds. These were written for graves and memorials for those who died in battle. The full epitaph included a heading, "On Some who died early in the Day of Battle Went the day well? We died and never knew. But, well or ill, Freedom, we died for you." Another of Edmonds' epitaphs is, "When you go home, tell them of us and say, For your tomorrows these gave their today."
The basic premise of this film inspired the 1975 Jack Higgins novel (and later a film) entitled: "The Eagle Has landed."