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.
Answer: There has never been prohibition in England. There are many reasons for running an underground distillery. It would be a way to avoid things like government regulations, safe distilling methods, alcohol content limits, taxation, fix pricing, and so on.
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