Episode #3.4 - S3-E4
Continuity mistake: The show opens with an elk grazing, a shot is fired and a deer falls dead on the ground. The antlers are different - not those of an elk. (00:00:20)
Episode #3.4 - S3-E4
Factual error: John says that he has found plans in the British Library. It was only renamed the British Library in 1973. Before that it was called the British Museum Library (or commonly just the British Museum) and nobody called it the British Library.