Factual error: A character is referred to in German as a she-devil, which is given as "sie teufel." This is German for the two words "she" and "devil" but not for the word "she-devil", which is "Weibsteufel." Or just "Teufelin." (00:32:15 - 00:33:20)
Factual error: During the fete sequence at the railway station there is a green van with the registration number YRL61C. Father Brown is set in the 1950s and C registrations were issued to vehicles first registered in 1965.