Factual error: Florence Carrington is killed on the train while she is leaving London for the weekend. When Poirot and Hastings examine the newspapers she could have been looking the day she was killed, the headline of "The evening news" in Poirot's hand announces the world record set by Malcolm Campbell at Bonneville Salt Flats in Utah, which happened on 3 September 1935, a Tuesday. (00:27:40)
The Murder of Roger Ackroyd - S7-E1
Factual error: A few drops of acid are dropped on a penny and the liquid bubbles (colorless liquid) as the acid eats its way through the penny. The penny is mostly copper. Any acid that can react with a copper will also produce a bright green to bright blue solution of dissolved copper, which is not the color seen. (00:05:20)
Suggested correction: Not necessarily. It depends on the acid and its strength. A weak acid may only oxidise copper to a monovalent state (Copper (I)) (which is colourless) rather than its divalent (Copper (II)) state which produces the blue solution.
Dumb Witness - S6-E4
Factual error: Spoiler. Police Sergeant Keeley tells Poirot that Doctor Grainger died of carbon monoxide poisoning. The killer turned the natural gas in the bedroom and did not light the heater. This would result in the room filling with natural gas, not carbon monoxide. (01:17:30)
Suggested correction: Surely it was coal gas at that time, before we all converted to natural gas?
The product of coal gas is still methane, which is CH4. It may contain tiny volumes of CO but the gas asphyxiation would still have come from methane, not carbon monoxide.
Factual error: Poirot smells and very carefully tastes a drink and says, "Potassium cyanide." It is impossible to distinguish between potassium cyanide and sodium cyanide (the other common cyanide) by this method. In addition, there are another less common cyanides that would smell and taste the same as potassium cyanide. (00:16:01)
The Million Dollar Bond Robbery - S3-E3
Factual error: The stock footage of the Queen Mary coming back from the US and docking in Southampton is not in black and white, and it certainly is more recent. The crowd wears colorful clothes, no hats, neon lights are used for the building illumination, and the cars parked are of modern design. It's a post-WW2 world, not 1936. (00:38:40)
The Million Dollar Bond Robbery - S3-E3
Factual error: As the title of the episode says, it's a million dollar robbery, in bonds. Problem is, as seen when the bag is loaded, the million is in 50 dollar bonds, which was the lowest single denomination for Liberty Bonds. 20,000 big bond notes would never fit in that bag, and would weigh a lot! Funny mistake, considering that the reality of 'weight' of a sum is a problem in many movies dealing with regular dollar bills, but bonds would have much fewer limitations as for the denomination of a single note (could have been a pile of bonds worth $10,000 or $5,000). (00:19:50)
How Does Your Garden Grow? - S3-E2
Factual error: Poirot and Miss Lemon go to the riding school to meet the solicitor of the deceased. Parked in the road right as the camera pans, and featured for a few seconds, is a car Morris Eight series II, a 1938 model while the episode (as made abundantly clear by the fair invite and banner) is set in 1935. (00:28:25)
The Mysterious Affair at Styles - S3-E1
Factual error: Poirot is taking a break from the prosecution' speech and is walking with Hastings, explaining to him Mary Cavendish's jealousy. In the street, they pass by a truck (registration plate MR 5496) that is a Morris-Commercial 1-Ton model. Morris began productions in the early 20s, and we are in 1917 for this episode. (01:17:45)
The Mysterious Affair at Styles - S3-E1
Factual error: At the local food store, Poirot is talking with the shopkeeper. In the background are plenty of food packages that show the great care for authenticity that is a mark of the series. I feel like disputing at least a couple; the Polly box with a parrot is a Taormina American-made can that should be a product of the 20s, and the Brown and Polson's Patent Corn Flour has a claim on the box that says "65 years world-wide reputation." The patent is a 1856 one and the annexed name is from 1859 (previous ads with established date show that year as the one they started counting from); in 1917 the box would have not said "65 years", it hadn't even reached 60. (00:19:20)
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)
Factual error: The basis of the blackmail is based on the Japanese invasion of Manchuria because howitzers were supplied to bombard Shanghai. Shanghai is not in Manchuria. (00:35:41)
How Does Your Garden Grow? - S3-E2
Factual error: At the very beginning of the episode, Katrina visits the Soviet embassy. It is written in big letters; "Union of the Soviet Socialist Republic", while the correct official name was "Union of Soviet Socialist Republics." (00:01:45)
Wasps' Nest - S3-E5
Factual error: When John Harrison check out of the organizer, the days of the week are wrong for a 1935 setting (September 24th is a Monday, etc), looks like a 1934 one. (00:12:00)
The Adventure of the Western Star - S2-E9
Factual error: Assuming the episode is in line with the others of the season and it is set in 1935, a few vehicles shown are slightly too recent. The plane waiting for South Africa is a Beechcraft Model 18 (first produced in 1937), the train going to Yardly has a SR Q locomotor first produced in 1938, and the truck that slows Japp down before getting to the airport is a Bedford M-Type, a model first produced in 1939 (the specific one used in this episode is from 1947).
The Kidnapped Prime Minister - S2-E8
Factual error: The calendar behind Japp in Scotland Yard places November 13 as a Tuesday, but that is wrong for 1935, when the story is set (the whole season consistently goes with 1935 historical facts, Poirot in this episode makes a reference to "the Dutch", and the newspaper page Hastings shows up with at the end of the episode talks about the notorious gangster's death, happened that year). It was a Wednesday in 1935, to be Tuesday it should have been 1934. (00:34:00)
The Kidnapped Prime Minister - S2-E8
Factual error: At the end of the episode, during the fitting of the jacket with monsieur Fingler (last role of character actor Milo Sperber), Hastings is reading a newspaper prop sporting a doctored first page (the real headline, which was about Italy, is replaced by the fake PM speech) of The Daily Express based on the real Friday October 25th, 1935, which is wrong in month and day of the week (the appointment was on Thursday and it's supposed to be November going by the various calendars seen throughout the episode). (00:51:00)
The Kidnapped Prime Minister - S2-E8
Factual error: Poirot in this episode has to save the Prime Minister, kidnapped before he could attend the League of Nations Disarmament Conference. This episode is set in November (the previous of the season in October), but it can't possibly be 1935, since the Disarmament conference happened between 1932 and 1934. It makes mention of the PM being vital to have at least a chance at preventing Germany's rearmament, with Hitler withdrawing Germany from conference and League of Nations entirely in October 1933. It should be noted though that the conference happened in Geneva and not in Paris like it's described here. The original material did not have this sort of inconsistency since it was set to happen much earlier in the century and for the Treaty of Versailles, where Paris would have been the correct destination. Both short story and adaptation have as prime minister a fictional "David MacAdam", with him designed to be a stand-in for David Lloyd George, just recently replaced as PM.
The Adventure of the Cheap Flat - S2-E7
Factual error: Agent Burt brushes off Poirot's question saying "When will you guys understand there is no such thing as the Mafia, the Black Hand or the Cosa Nostra?" The last term he uses, while not impossible (since members of the organization were indeed referring to it as such) is a huge improbability, considering that officially FBI (and certainly the general public Burt is lashing at) came to know the real name (adapted in "La cosa nostra") only decades later with the Valachi investigations. (00:24:05)
The Adventure of the Cheap Flat - S2-E7
Factual error: When Poirot asks O'Brian about unsolved crimes with young couples as suspects, he says "There's that Bonnie and Clyde of course, but they're at large somewhere in the American Midwest", to which Poirot replies "And let us hope that is where they remain." Bonnie and Clyde were killed in Louisiana on May 23, 1934. The episode is set in October 1935. (00:12:20)
The Disappearance of Mr. Davenheim - S2-E5
Factual error: At Poirot's, Hastings browses a copy of Speed magazine - but it's the August 1936 issue. The story is set in mid-October 1935 (not just for consistency with the rest of the season, but also because the newspaper brought by Hastings towards the end mentions Duff Cooper as Financial Secretary for the treasury, which is a position held in that year before the elections - which are also mentioned). (00:18:30 - 00:43:40)
