According to the cover on the DVD of this film, "The story is based on a true incident in which an Air Corps crew deliberately sacrificed their lives to save an English village of no strategic importance." But, I could find no further reference to provide more details or to substantiate that statement. If there is such a connection, it most likely would be just with the very end of the movie in which that plane crash occurs. It's highly unlikely that it would be based on the plot of the film, however, or surely there would have been a book or story written or printed somewhere about the people and incidents of the main plot.
"A Yank in London" was the film's title when it was released in the States after its original showing in the U. K. as "I Live in Grosvenor Square." It debuted in March of 1945 while the war was not yet over in Europe. Although it doesn't specify the date, it was in the months leading up to the D-Day Landing in Normandy on June 6, 1944.
The build-up of American and other forces for the invasion had been going on for some time. Allied servicemen were being billeted in English homes and manors; and military units had taken over whole estates and buildings. This film gives a good portrayal of that, and, in this case, of the affability and congeniality of many of the Brits, including the landed aristocracy with and toward their "guests." While all of this was taking place, the Allied air forces were continuing to make bombing raids into Germany to cripple its war capacity and try to bring it to the peace table.
So this story develops as a sort of love triangle when an American Army Air Corps sergeant meets and is housed with the Duke of Exmoor and his family. The duke's niece, Lady Patricia Fairfax, is the female in this triangle, and the other male is Major John Patterson, a boyhood friend and close friend of the family. Patricia and David are engaged, but John and she fall for each other after a while. By stretching one's imagination, it's possible to think there is a real attraction between Patricia and John, but it takes that because it otherwise isn't apparent in the film. This might be a way of showing something of a more mature relationship than might be with a young GI and a young British lass. But, still, neither Anna Neagle nor Dean Jagger display any real sense of falling for one another. Rex Harrison plays Major David Bruce, and while his role is better, it's also not terribly convincing.
The best performance in the whole thing is by Robert Morley as the Duke of Exmoor. Elliot Arluck seems a bit overboard as a stereotypical gum-chewing, boisterous Yank from New York. He's Sgt. John's sidekick and fellow crewman who has also been on rehab leave with John.
This film has a couple of strange twists - Major Bruce gets a short leave from duty to run for a vacant seat in Parliament. And, toward the end, he gets a short leave while in uniform and his paratroop unit is waiting the word to take off on its invasion flight. The screenplay can't handle well the sudden change in heart of Sgt. John for not wanting to go between David and Patricia. So, John goes back into combat flying bombing missions as a gunner, and his plane crashes and explodes on its return with two engines out. The film shows him assisting the captain and pulling up to keep from crashing into the church tower of a small English village. After a memorial service on the ground, Major Bruce joins his unit and they all hit the silk (that's we airborne guys' lingo for jumping) supposedly during Operation Overlord, i.e. D-Day.
The film's rather slow and tame, with not much life in it except for the portrayal of the local Brits and the duke's family and estate. A somewhat better and similar story was made in 1956 by 20th Century Fox. "D-Day the Sixth of June" starred Robert Taylor and Richard Todd with the love triangle around Dana Wynter. That story also had a different ending from this film and also from the ordinary. But, it was a better scripted and believable romance and war story. It didn't show the British amiability of its hosting the Yanks like this film does, but the story seemed more plausible. That movie was based on a 1955 novel, "The Sixth of June," by Lionel Shapiro.
Here are a few favorite lines from this film.
Duke of Exmoor, "When was the last time you packed?" Parker, the butler, "The Boer War, your grace."
Sgt. John Patterson, "All this excitement for one member of parliament. It's a good thing you don't elect your kings over here."
Pub patron, "Well, the government may be all right for now, but what about later on?" Innkeeper, "Ah, you ain't voting for later on." Pub patron, "No? When shall I be then?" Innkeeper, "Later on." Pub patron, "I may not be here then." Innkeeper, "When?" Pub patron, "Later on." Innkeeper, "Well, what're you worrying about?"