Revealing mistake: The phone book has a LMS logo on the page edges in the close-up where we see Poirot actually flip through - the logo disappears when he is moving the book in the rest of the scene. (00:16:10)
Revealing mistake: The stuntman smashing through the window is quite obvious - he does not even have the hair styled like Hastings'. (00:31:30)
Revealing mistake: As he scolds Hastings for his pancreatic hullabaloo, Poirot drinks his tisane from an empty cup. (00:02:55)
The Adventure of the Western Star - S2-E9
Revealing mistake: Japp is waiting for Van Braks to make his move, and when he is hopping on a taxi for the airport, he begins to tail him. When the car moves, reflected in the door is a modern No Parking cone in bright yellow (incidentally, they also pass by a parked car with a FUU 692 plate that is a bit too recent for the series, being an Austin Big 7, first produced in 1937). (00:41:05)
Answer: He definitely says "Belgian", but the subtitles get it wrong and show him saying "American."
Wblank71