One character whom some viewers harbour suspicions about is Ian Buckells (Nigel Boyle), the superintendent in charge of the Hillside Lane murder squad.
However, some viewers have identified a number of other clues which mean Buckells could yet be revealed as the “fourth man”.
With the sixth season of Line of Duty nearly coming to an end, speculation remains rife as to the identity of “the fourth man”.
Buckells had enjoyed a romantic relationship with Devereux, having intervened when she was arrested for assault years earlier.