Vera Atkins's Certificate of British Naturalisation has the U.S. spelling 'Naturalization'.
Vera Atkins was not aware of Noor Inayat Khan's fate until after the war, when she visited France and Germany to ascertain details of the losses of her agents. The movie wrongly depicts Atkins, with Virginia Hall, breaking the news of Noor's death to Noor's mother before the end of the war.
Colonel Buckminster is wearing the shoulder insignia of a Major.
Virginia Hall refers to "CARE packages" during the war. CARE packages were not created until 1946 by the Cooperative for American Remittances to Europe (CARE). However, "Care Package" is a generic term for such packages, the most prolific of which were those distributed via the International Red Cross.
All the cars seen in 'London' are very American in style. The film was made in Hungary and the U.S.
When Philomene arrives in Perpignan, the train tender is seen in the background as she walks past. The tender clearly has Hungarian markings on it for the Hungarian nostalgia train H-MNOS.
As the German troops occupy Vichy France in November 1942, you can see a Panzerfaust in the middle of one of the Kubelwagens driving through the streets. The Panzerfaust did not enter service until August 1943.
All the cigarettes seen appear to be 100mm American-made types. These were not introduced until the 1960s. Before that, "regular" cigarettes were 60mm and "king sized" were 80 mm.
In a night scene in the spy training camp, the atmos track features cicadas and a classic American train whistle. Neither of these could possibly be heard, given that the camp is supposed to be in Scotland.
Virginia travels to Perpignan, France, to cross the Pyrenees into neutral Spain. The movie shows the Pyrenees as dramatic, jagged peaks similar to the Alps. In reality, the southern Pyrenees near Perpignan are gentle, rolling hills.
The house at "13 Baker Street", which plays the part of SOE headquarters, is a rustic stone building that looks to be a rural building on a narrow lane. This is totally incongruous with the actual Baker Street, which is a large street and major thoroughfare in the centre of London.
Trainee spies are instructed not to reveal their own names but only to use their code names. Despite this, the controllers continue to refer to Noor by her real name throughout most of the film.