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 #3.2 - 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 #3.2 - 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.
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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