
Continuity mistake: When Gertie and Joey make their escape running down the stairs of the hall, they pass by a couple (she has a white hat and a blue dress). When Poirot and Japp run after them, the same couple has jumped back several meters. (00:43:00)

Continuity mistake: The cream colored shoes of the Lady are prominently featured in the finale. When the actress has to run, not only are the heels replaced by modern tennis shoes, but they're black, in contrast with her white stockings. (00:46:40)

Factual error: Poirot is cycling through Wimbledon; he passes by a house which has a definitely non-1930 car in the yard, and a yellow alarm box on the first floor. (00:18:20)

Revealing mistake: The stuntman smashing through the window is quite obvious - he does not even have the hair styled like Hastings'. (00:31:30)