Factual error: A woman who was sentenced to death while pregnant, as Long Susan was, was never hanged. Her sentence was stayed until she gave birth and then always commuted to imprisonment. Most such women were released after only a few years.
Factual error: H Division moved into a new station house in 1897. This did not happen until 9 March 1970. In previous episodes the station is factually incorrect as well, as the previous station was deemed unfit for purpose in 1882, and they obtained the land of the former Garrick theatre in 1886 and a new station started building but it was not completed until 1890/91.
Factual error: The Risaldar-Major is in command of the Bengal Lancers. The commandants of Indian regiments were actually British, as were many of the officers. The Risaldar-Major was the senior Indian officer of a cavalry regiment, but held a similar position to the Regimental Sergeant Major in a British regiment. He certainly did not command it. Although commanding great respect, he was junior to all the regiment's British officers.
Factual error: The depiction of the hanging is completely inaccurate. By the 1890s, the gallows at Newgate were housed in a room within the prison, not in the courtyard. Prisoners' wrists and legs were pinioned before they were hanged, not left free as depicted. The long drop was used in Britain from the 1870s, not the short drop depicted. The large knot depicted was not used in Britain (although it was in America) ; a simple sliding loop was actually used, and this was positioned under the jawbone at the side of the neck, not at the back of the neck, which would quite probably not have broken the neck, leaving the person to strangle to death.
Factual error: As Colonial Secretary, Joseph Chamberlain had no authority over India, which was not considered to be one of the colonies. There was a separate Secretary of State for India, a position held in 1897 by Lord George Hamilton.
A White World Made Red - S4-E3
Factual error: DI Reid is sworn back in as a constable by DI Drake. Only a magistrate can swear in a police constable, which is a judicial office.
Men of Iron, Men of Smoke - S4-E4
Factual error: In the flashback to the courtroom scene at the beginning, there is a gavel sitting before the judge. British judges have never used gavels.
Men of Iron, Men of Smoke - S4-E4
Factual error: One character refers to another as a wanker. The first recorded usage of this term in a sexual sense is in 1950 and as an insult in 1972. The episode is set in 1897 and its language is consistently that of the time; it doesn't use modern language.
