Line of Duty fan theory connects DCI Joanne Davidson to last season’s John Corbett

Theory is based on a blink-and-you’ll-miss-it detail from episode one

We’re still only two episodes into the sixth series of Line of Duty, but already the fan theories are coming thick and fast.

BBC One’s hit primetime thriller has added Kelly Macdonald to its cast for the new run of episodes, playing DCI Joanne Davidson.

From the very first episode, it seems as though Davidson is hiding something – so when AC-12 start investigating her unit, Davidson is a prime suspect for the series’ new bent copper.

However, some fans believe they’ve already worked out exactly what Davidson’s hiding, and have claimed to link the character back to Stephen Graham’s John Corbett, who appeared in series five.

In episode one, there is a scene set in Davidson’s apartment in which the character is seen looking at a photograph of her and another older woman, presumed to be her mother, which prompts her to smash a glass in anger.

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While the identity of the woman in the photo remains unknown, some fans have suggested she bears a resemblance to the photo we’ve seen of Anne-Marie McGillis, the biological mother of Corbett whom Hastings once used as an informant.

People have speculated that Davidson could in fact be related to Corbett, and may be posing as a dodgy copper to help bring down the OCG in revenge for her family’s death.

Whatever the explanation, the reappearance of Corbett’s widow, Steph, in the latest episode, suggests that Corbett’s storyline remains fresh in the writers’ minds.

Meanwhile, some Line of Duty fans also believe they have guessed the identity of a mysterious voice heard in an audio recording on the phone of murdered journalist Gail Vella.

Also, a background detail in episode two was also spotted by some eagle-eyed viewers, revealing that DI Kate Fleming (Vicky McClure) knows more than she’s letting on.

Line of Duty continues at 9pm on BBC One every Sunday.