The murky world of AC-12 is awash with chameleonic coppers. 

So the question of who “H” really is – man or woman, dead or alive, one person or more  – will have even the most astute Line of Duty watchers among us caught up in a dizzying web of intrigue. 

We know he or she is a top dog police officer with direct links to organised crime. But where writer and master of misdirection Jed Mercurio is concerned, anything else is a wild guess.

So we’re taking the lead from the show itself and trusting no-one. Not even that there’s an obvious link to the letter H at this point, or that H is a he (as clues suggest).

With all bets off, we put a line-up of suspects to the test (warning: contains spoilers from previous episodes).

The case for: Ted Hastings’ behaviour has become increasingly fishy over the course of series 5, and if we were a DI, we’d definitely be hauling him in for a chat. We’ve seen the superintendent grapple with money problems and a messy split from his wife. Are these signals that his double-life is unravelling? Or do they hint at pressures sending him to the dark side? If Hastings is “H”, he needs to be a bit more sophisticated about how he handles his laptop, that’s for sure. 

The case against: We know Hastings has a short fuse. Could he really handle the weight of being a cool and collected criminal mastermind? Also this typo kept us guessing. And for a plot as left-field as Line of Duty, he seems almost too obvious.

Stylist verdict: One to watch but we’re not convinced.

The case for: If there’s one thing we know about Kate Fleming, it’s that she has an excellent poker face. As an UCO, she’s flawlessly kept her cover in situations that would leave most of us in tatters. And in a TV series of enormous twists, this could be the most shattering of all.

The case against: There’s no evidence at this point. In a world where bent coppers come ten to the dozen, DI Fleming has always appeared to be the moral heart of AC-12. 

Stylist verdict: It would be a HUGE, mind-blowing leap; yet that’s what Line of Duty is all about.

The case for: Wild card Steve Arnott always dances a fine line between criminals and coppers; he plays both sides off one another with finesse. He’s a curve-ball choice for H, naturally, but could the fact that he seems above corruption be part of the deep and intricate cover? Remember, this is a man who was hung out to dry by his colleagues right at the beginning of the series. 

The case against: Like Fleming, Arnott has always seemed like he’s one of the rare good ‘uns. He’s risked life and limb to act with integrity in the past. Plus, he’s arguably not senior enough to leak high-ranking insider info to the OCU. 

Stylist verdict: An outside horse.

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.

Images: BBC Pictures