Episode #3.4 - S3-E4
Continuity mistake: The show opens with an elk grazing, a shot is fired and a deer falls dead on the ground. The antlers are different - not those of an elk. (00:00:20)
Episode #3.4 - S3-E4
Factual error: John says that he has found plans in the British Library. It was only renamed the British Library in 1973. Before that it was called the British Museum Library (or commonly just the British Museum) and nobody called it the British Library.
Episode #3.5 - S3-E5
Factual error: All of Tommy's former men salute him. As a sergeant-major and not an officer he would never be saluted. This is drummed into all soldiers and they'd never do it, even in civilian life. Not only is it against regulations, but many NCOs would take it as an insult.
Episode #3.6 - S3-E6
Factual error: The locomotive used to pull the train is a LMS Black 5. This class of locomotive was not built until 1934, 10 years after the year this episode is set in. (00:32:25 - 00:32:55)
Episode #3.6 - S3-E6
Continuity mistake: Michael picks up the cash from the table. After Polly speaks to Tommy she turns around to take the money out of Michael's hand; in the shot Michael is holding the cash in his lap with his jacket off, but when Polly takes the cash it shows her hand taking the money from Michael with him wearing his suit.
Episode #3.6 - S3-E6
Factual error: Tommy says that the Chief Constable of Birmingham has issued a warrant for the arrest of Arthur, John, Polly and Michael. Only a magistrate or judge can issue an arrest warrant. The senior officers of the Metropolitan Police were sworn in as magistrates, but not those of other forces.
Factual error: Jessie Eden is described as a shop steward. A shop steward is the senior part-time trade union official in a particular workshop or department, who also has an ordinary job in that shop. Jessie appears to be a full-time official and covers a number of factories. She would actually be referred to as a trade union organiser.
Factual error: It's Christmas Eve 1925. Tommy and his son leave a mince pie for 'Santa and Rudolph', but there was no reindeer called Rudolph until the 1930s. The character's author hadn't even graduated by 1925, and only began writing a book about a red-nosed reindeer in 1939.
Factual error: Lord Stamfordham has a paper before him headed 'London Constabulary Police'. There was no such thing.
Character mistake: Ada is listed on the portraits of The Company officers as Mrs Ada Shelby. She is actually Mrs Ada Thorne.
Factual error: Arthur is "deputy vice-president" of the Shelby Company Ltd. This is an American position title that would never, ever have been used in 1920s Britain.
Continuity mistake: Tea leaves are visible to the top of the cup during the reading's close-ups, but the cup is clean each time the view switches to full screen. (00:29:30)
Visible crew/equipment: An iPhone being held by someone is visible through a window in the top left of the screen during the decoy vehicle scene near the beginning of the episode.
Factual error: Kenya tea chests are marked KTDA. (Kenya Tea Development Agency). This did not come into being until the early 1970's.
Factual error: The British Army had no female soldiers in the mid-1920s. Queen Mary's Army Auxiliary Corps was disbanded in 1921 and no women served in the army from then until the formation of the Auxiliary Territorial Service in 1938.
The Company - S4-E6
Factual error: Tommy makes a call during the episode to the USA, there was no system for international calls in 1926 for the general public, that was only introduced in 1927. (00:33:30)
Factual error: The fact Colonel Younger is black and this may be an issue socially is implied several times (meaning the series acknowledges his ethnicity), but it never seems to be seen as surprising that a black man is a colonel in the British Army in the first place. While there were a small handful of mixed-race junior officers in the army in the First World War, there were no post-war black regular officers (it was actually against regulations at the time) and no black officer would hold such a senior rank until long after the Second World War.
Character mistake: Several times Tommy addresses Sir Oswald Mosley as Mr Mosley instead of the correct Sir Oswald. Mosley never corrects him, which given his snobbishness portrayed throughout the series seems highly unlikely.
Factual error: Mosley is portrayed as forming the British Union of Fascists in 1929 or 1930. In fact, he formed the New Party in 1931. The party failed to win any seats in the 1931 general election (with Mosley himself losing his seat) and Mosley then formed the British Union of Fascists in 1932.
Factual error: In the House of Commons, Tommy refers to an unseen Tory MP as "My Right Honourable Friend" and as "the member for Epping." The former address is only used for Privy Councillors of the speaker's own party (Tommy is a Labour MP); MPs of other parties would be "the Right Honourable Gentleman." Winston Churchill was MP for Epping at the time and Tommy's secretary later says Churchill is in America, so he can't possibly be addressing the member for Epping.
