In 1943, a plan was conceived which would trick Adolf Hitler.
The plan is given the name 'Operation Mincemeat'.
At the height of World War II, the allied British forces need Germany to believe they are invading Greece instead of their true target, Sicily.
British intelligence devises a plan to float a corpse carrying fake documents into Spain, hoping that the Nazis will intercept the message and then leave Sicily unguarded.
Knowing that the Germans will scrutinise every detail of the body, great care is taken in devising an airtight backstory for the fake fallen soldier.
Colin Firth, who stars as Ewan Montagu said of the true story, "we learn that spycraft is to sometimes have ideas which are completely bonkers. Because the more logical you are the more people can guess what you're about because you can decode logic. You can't really decode bonkers."
Firth stars alongside Matthew MacFadyen as Charles Cholmondeley, as if the film wasn't British enough already, it stars Mr Darcys from two different adaptations of Pride and Prejudice.
Adding further to the Britishness of the film is that James Bond author Ian Fleming, played by Johnny Flynn, played a role in the operation. Prior to writing Casino Royale, Fleming was a key part of Operation Mincemeat.
"It's almost like something out of a James Bond novel," remarked Flynn at the premiere.
Operation Mincemeat is an incredibly solid film. It doesn't waste time being overly flashy or take any major risks with its filmmaking.
This simplicity and straightforwardness could be mistaken for being tedious if you're not on board with the film, but if the plot intrigues you, you'll find yourself captivated.
The film fits tidily alongside similar flicks like Darkest Hour or The Imitation Game.
If you go in expecting a British WWII spy film, you're getting exactly what it says on the tin.