Episode #2.4 - S2-E4
Corrected entry: Tommy Shelby says that he is exporting whisky to Halifax, Nova Scotia, which is under prohibition, as is all of Canada and the United States. There was no prohibition in Canada. Not a mistake a businessman as astute as Shelby is likely to have made, especially as he's based his whole business plan on it.
Correction: This is incorrect. In March 1918 Ottawa stopped, for the duration of the First World War, the manufacture and importation of liquor into provinces where purchase was already illegal. However, prohibition was too short-lived in Canada to engender any real success and was not strongly enforced. Individual provinces repealed the law over the next 5 years starting with Quebec in 1919 through to Nova Scotia in 1930.
Episode #2.2 - S2-E2
Corrected entry: Solomon says he killed an Italian soldier in the trenches during the war. Italy was a British ally during WWI. While Italy fought the Austrian-Hungarians, they did not fight in France or Belgium.
Correction: Italians did fight in France and British soldiers did fight in Italy and in the Balkans alongside Italians, so many places where they could have met. Solomon never said he was killing an enemy, just an Italian.
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.
Correction: Except Season 2 occurs in 1921-22, well after Prohibition ended in Canada.