The Mysterious Affair at Styles - S3-E1
Factual error: The movie opens with Hastings watching a news film about the "New Flanders Offensive." It says that on "7th June 1917 General Haig attacks Ypres", but at the beginning of the year Sir Douglas Haig was promoted to Field Marshall. A news propaganda reel would surely have called him with the appropriate title. (00:00:35)