Who are they?

Chief Constable Derek Hilton: According to Hastings, the mystery of H began and ended with the apparent suicide death of Hilton in series 4. Hilton had long held ties to organised crime, and his cover was eventually blown. It’s unlikely he’ll come back from the dead (even for Line of Duty, that’s stretching credibility) but given H is still active, he’s evidently either passed on the mantle to another copper-gone-bad (an underling perhaps), or the real H has taken over.

DCS Les Hargreaves: Another bent copper that has come a cropper, DCS Hargreaves came to an untimely end as his shady shenanigans with the criminal elite were unmasked last episode. But it seems unlikely that a slick operator like H would risk blowing his cover by attending the scene of a raid OR that LoD producers would abruptly kill off H this soon into series 5.

DCI Roz Huntley: Last seen in series 4, DCI Huntley (played by Thandie Newton) certainly lost sight of her moral compass. The last word from her was that she was being sentenced to 10 years for manslaughter and perverting the course of justice. As a cop boss, she was wayward, sure, but could she be ruthless and violence enough to be H? And manage all direction of the OCU from behind bars? The jury’s out.

Alison Powell: She’s the woman in charge of the car-crash Operation Peartree, and she’s also been very reluctant to help out AC-12 with their investigations. A newcomer to the line-up of H suspects this season, Powell has shown herself to be a slippery customer indeed to date. But is she shady enough to actually be the top boss, or is she simply protecting him or her?

Stylist verdict: None of this lot seem likely to be the ultimate H, although DCI Huntley could be an inspired choice if the plot writers played their cards right. And we’ve got our eye on Powell, too… watch this space.

Line of Duty season 5: Who actually is H? Is it a woman?