Factual error: This episode happens on the first days of November 1935. During the 5th of November fireworks Hastings, Japp and Poirot walk at night through streets with plants prospering and in full green, and the same happens during the visit to the golf course.
Factual error: As Japp and his moustached pal visit the nightclub in search of Major Eustace, the song "Hindustan" is executed. While it is a song perfectly believable for the year (stated as being 1935) since it was written in 1918 and a huge hit, the version played here is quite a bit different, sounding a lot more like the upbeat version heard first in the Rosemary Clooney-Bing Crosby album "Fancy Meeting You Here", which had other classics reworked for the duet formula with added lyrics - exactly like in the back-and-forth heard here between the singer and the band. Said album came out in 1958, though. (00:30:20)