Starring: James Norton, Morven Christie, Robson Green, Tessa Peake-Jones
Episode #8.5 - S8-E5
Other mistake: We are told several times that the "Special Reserve" is kept locked in Mr. Palmer's office. When Anna comes to the bar to "see" it (and put the poison in it), it is in plain sight on the shelf behind the bar, and her husband hands it to her.
Episode #3.5 - S3-E6
Continuity mistake: Sidney is attending a pre-wedding dance in the camp he is visiting wearing a light colored shirt. When he leaves the dance floor to chat with other attendees, he is now wearing a green sweater over his shirt.
Episode #7.5 - S7-E5
Trivia: The Matron is called Fletcher. Louise Fletcher played the chief nurse (and a similar character) in "One Flew Over the Cuckoo's Nest."