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.
Factual error: Albert Garrity tells Father Brown about himself and his late wife meeting "Mr and Mrs Weston" on Mayday bank holiday in 1931 and it was the wettest mayday for twenty five years. Mayday wasn't made a bank holiday until 1978.
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."