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
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 #3.4 - 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 #3.2 - S3-E2
Factual error: Patrick Jarvis mentions Tbilisi. Nobody in Britain would have called the city by that name in 1924; it was still always referred to as Tiflis.
Episode #3.3 - S3-E3
Factual error: Tommy refers to Istanbul. It was always still called Constantinople in the West at that time and would be for several more years.
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 #3.2 - S3-E2
Factual error: Father Hughes says that Admiral Hall may be detained in the House of Lords. Admiral Hall, although knighted, was never ennobled and thus did not sit in the House of Lords.
Episode #3.3 - S3-E3
Factual error: Grace suffers a gunshot wound to the upper left chest in the previous episode, and episode three reveals she died. The bullet would have passed under the clavicle and would have missed the axillary artery and all other major blood vessels. This wound should not have been lethal, especially because Grace's family immediately called for an ambulance, so she would not have had to wait long for medical treatment. Most of her family members are military veterans who would have knowledge to provide the necessary first aid. (00:01:50)
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: The Russian grand duke is called Leon Petrovna. Petrovna (daughter of Petr) is a patronymic used by a woman. A man would use Petrovich (son of Petr).
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 #3.1 - S3-E1
Continuity mistake: At the wedding, Arthur leaves the table looking for Tommy and Grace, leaving his suit jacket. The next scene, he appears at Tommy's door wearing the jacket. (00:14:20 - 00:15:30)
Episode #3.2 - S3-E2
Continuity mistake: John and Polly are talking in his office. He is wearing a ring on his left hand, then a few seconds later he is not.
Episode #3.1 - S3-E1
Continuity mistake: When Michael and Charlotte are alone together, the size of the flame on the candle differs depending on who is in shot.
Episode #3.1 - S3-E1
Visible crew/equipment: While Tommy is making a toast at the dining table, a boom mic can be seen at the top of the frame for a brief second. (00:19:30)
