In the opening scene Lassen has blood all over the front of his shirt after killing a bunch of the German sailors. After they blow up the German patrol boat the blood is suddenly gone from Lassen's shirt.
"Mack The Knife," from Bertolt Brecht's leftist play The Threepenny Opera, plays twice in Nazi company. Brecht was a communist who fled Nazi Germany, and The Threepenny Opera was in fact banned by the Nazis for being "degenerate art."
During the raid to steal the freighter which is fully loaded and further weighted down with extra armor the men tow the freighter with only one tugboat, despite having stolen two more tugboats. Once they were clear of the harbor and its breakwater they would have needed the two other tugboats to tow the ship because of currents and weather.
During a German air raid over London, Prime Minister Winston Churchill is staying at his official residence located at 10 Downing Street in London, risking being killed in the bombing. During the war and especially during air raids, Churchill and all essential British military and government staff worked and slept in a huge underground shelter complex in London.
When Henry Cavill is talking to Cary Elwes about the mission, he reaches into a box of cigars. The cigars are Fuente OpusX, which weren't produced until 1995. Churchill also only smoked Cuban cigars, usually Romeo y Julieta.
The Duchessa and various other boats in the movie, like the tugboats, appear to be quite a bit newer/more modern than the film's 1940s setting.
Gustavus "Gus" March-Phillipps, as seen here, spelled his last name with three 'P' and not two, as the movie claims.