There are repeated references to Churchill as "Sir Winston". Churchill didn't receive that title until nearly a decade later from when this is set when in 1953 when Elizabeth II invested him with the Order of the Garter thus only then making him "Sir Winston Churchill".
Bar-le-Duc is a 3 hour automobile drive from Paris. It would not take anyone to drive "through the night" to get there. Also, it is nowhere near the France-Germany border.