The portrait of Alistair Blunt and his wife in the board room is in the style of Tamara de Lempicka, one the most fashionable portrait painters of her generation and a leading representative of the Art Deco style. Another such imitation appears in the episode The Underdog.
The flashback scenes take place in 1925.
The newspaper read by the Lichfield Court porter contains the headline "The Reinsdorf Explosion". This refers to the explosion of at least 27 tons of munitions at the Westfalian-Anhalt Explosive Works in Reinsdorf, Saxony, Germany, the only plant in the country which was permitted to produce explosives under the Treaty of Versailles, on June 13, 1935. More than 100 people were killed with over 400 injured. A memorial service in Reinsdorf on June 18 was attended by Adolf Hitler, Hermann Göring and Joseph Goebbels.
Alfred Biggs is reading The Hotspur #1 (September 2, 1933).
Poirot is reading the January 6, 1849 issue of "Punch" in Mr Morley's waiting room and "Classic Myth and Legend" (1912) by A. R. Hope Moncrieff in his flat.