Factual error: In series 1, Sergeant Moss says he and most of his men served in the First World War, but none of them wear any medal ribbons. In series 2, Moss has suddenly acquired three medal ribbons, but they seem to be made-up and are not relevant to the First World War. From series 3, Moss is wearing the correct three service ribbons for the First World War.
Factual error: Chief Inspector Campbell has been sent from Belfast. Belfast at the time was policed by the Royal Irish Constabulary, which had no rank of chief inspector.
Factual error: Throughout the show bottles of liquor have sprout dispensers attached to them. Sprout dispensers were not invented until the 1960s.
Factual error: Filter cigarettes weren't conceived until 1925 and not in common use until decades later. No self-respecting gangster would have smoked them.
Other mistake: There are multiple spelling mistakes in the sub-titles: Saltley is spelled Saltely, Balsall Heath is spelled Basall Heath, and Changretta in Italian would be Ciangretta.
Factual error: Filter cigarettes didn't appear before 1935, but here everyone seems to be smoking them.
Episode #1.1 - S1-E1
Other mistake: When detective Campbell is making his speech to the officers, the board behind him has dates ranging from 1966 - 1975.
Episode #1.1 - S1-E1
Factual error: Thomas' record says he received the King's Medal for Gallantry in the First World War. There was no such medal. It would have been the Military Medal.
Episode #1.1 - S1-E1
Factual error: Ada is watching a movie and when asked "tell me the man's name" says "Rudolph Valentino." Valentino was largely unknown in 1919, only appearing in bit parts. She is also eating popcorn. This was not done in movie theaters until the 1930, unless you brought your own. Only street vendors sold popcorn.
Suggested correction: This is from episodes #1.2 and two separate mistakes. But being "largely unknown" doesn't mean she couldn't know his name. And who's to say she didn't buy the popcorn from a street vendor? You don't see others eating popcorn, so there's no suggestion she bought it there.
He used the name Rudolph Valentino for the first time in 1921.
That's not true since he was credited as Rudolph as early as 1917.
Episode #1.3 - S1-E3
Factual error: When attempting to arrest Grace one of the supposed IRA men proclaims that he is taking her into custody "on behalf of the Irish Free State." The term "Irish Free State" was not a term used by republicans or generally until the Anglo-Irish Agreement which led to the end of the War of Irish Independence and the establishment of the Irish Free State in 1922. Anyone representing the IRA would have, when speaking English, referred to the Irish Republic at that time.
Episode #1.3 - S1-E3
Factual error: One of the men who approaches Tommy claiming to be representatives of the IRA sings the song "The Boys of the Old Brigade." The song is told from the perspective of an elderly veteran of the Irish war of independence which had only began in January of 1919 which had happened only 3 years before. The song was written by Paddy McGuigan of the band Barleycorn in the 1970's.
Episode #1.4 - S1-E4
Continuity mistake: Thomas and Grace are sharing a drink to celebrate her employment with the Shelbys. Thomas pulls out a cigarette, puts it in his mouth (correctly), and then turns to the camera to reveal a backwards cigarette. (00:43:00)
Episode #1.4 - S1-E4
Factual error: When Freddy and Ada return to Birmingham from London they are seen on a boat called Kennet. This is a wide boat (i.e. almost twice the width of a 7 ft narrowboat) which could not have made its way from London to Birmingham in 1919/20 as all of the locks were narrow locks (7 ft) at that time.
Episode #1.4 - S1-E4
Factual error: In 1919 Chapman receives £200 from the Russian Embassy, but diplomatic relations were not established until 1924.
Episode #1.5 - S1-E5
Continuity mistake: When Tommy enters the office where Grace is working on the books he steps forward, leaving the door open, to draw a black star on her ledger. When he turns to leave the door is shut. (00:03:40)
Factual error: Michael's impending 18th birthday is often mentioned as the time he becomes an adult and can make his own decisions. The age of majority in 1922 (and until 1970) was 21.
Other mistake: When Polly tells Ada about her two children being taken from her, she says Michael was 5 and "Sally" was 3. When she goes to the seance she says her daughter would be 18, but shortly after that Tommy finds Michael and he is 17. Also, when Tommy tells Polly that he found the records on her children, the daughter's name changes to "Anna."
Other mistake: The Birmingham police officer, Moss, is still listed in the credits as Sergeant Moss. He held that rank in Season 1, but in Season 2 he wears inspector's rank insignia. Campbell does address him as Mr Moss, the correct title for an inspector.
Continuity mistake: The first man to die in the ploughed field "execution" scene had the back of his head blown away by a gunshot. In the replay in next episode, his head shows no such effect.
Factual error: Major Campbell heads the Irish branch of the secret service, but reports to Winston Churchill, the Colonial Secretary. The Colonial Office had nothing to do with Ireland, which at that time was part of the United Kingdom.
