Line of Duty fans have spotted a grammatical error which they think could solve one of the show's biggest mysteries. The blink-and-you-miss-it moment came during last night's episode as viewers caught sight of a poster on the wall behind Acting Detective Superintendent Jo Davidson (Kelly Macdonald).
The sign read: "Please return all files once your finished with them Thank you!!!!" - with eagle-eyed viewers pointing out the misuse of the word "your" could be a major clue.
The grammatical blunder seems to tie in with other typos made by the mysterious person who has been secretly messaging Davidson on her lap top and fans think it could indicate the shadowy figure could be the one who put up the poster in the police station.
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