Line Of Duty: An Examination Of The Most Popular Theories – And How Likely They Are To Be True

We've done the detective work, so you don't have to.

There may be only two episodes left in the current of series of Line Of Duty, but fans currently have a whole load more questions than they do answers.

As a result, the internet is rife with theories as people watching at home do their best AC-12 impressions to try and solve the case - and most importantly, work out who the mysterious ‘H’ is.

Just a glance at Twitter will show you they range from the obvious, to surprising, to downright curveballs - so with that in mind, we’ve rounded up seven of the most popular to take a closer look at just how plausible they really are...


THEORY 1: Hastings is H

Let’s start with the big one, shall we?

A dodgy look in the closing moments of series four first floated the possibility that Hastings is the corrupt top officer who is pulling the strings of the organised crime group (OCG), and his actions over the most recent episodes have continued to build on the idea.


What people are saying:


  • Scenes have shown Hastings using his laptop directly after the OCG have been communicating with H
  • Hastings had his laptop destroyed after learning that Arnott had made contact with Corbett
  • Hastings spells ‘definitely’ as ‘definately’ - just as H does
  • He received a massive wodge of cash from Moffatt just days after the Eastfield Depot heist
  • He ordered Arnott and Fleming to attend the fake police ambush during the stakeout at the Eastfield Depot heist, suggesting he could have been trying to get rid of them before Hargreaves’ arrival
  • The man who visited McQueen at the brothel owned by the OCG bore more than a passing resemblance to Hastings
  • He has been shown seemingly trying to call McQueen

Likelihood: Sorry, but we’re just not buying it. Over the previous four seasons, Hastings has been a stickler for procedures and sticking to “the letter of the law”, and it feels like we’re being pushed way too heavily to conclude Hastings is H.

It is now so obvious that we’d actually be disappointed in writer Jed Mercurio if it were to be true, and given that Jed has never let us down so far, we’re ruling this option out.

Plus the fact, if Hastings was heading up some huge organised crime organisation, he’d surely be a hell of a lot richer than what he is right now.

THEORY 2: Gill Biggeloe is H

If Hastings isn’t H, then we need to consider who else it could actually be, and one of the most popular theories points the finger in the direction of AC-12’s former legal counsel, Gill Biggeloe.


What people are saying:


  • In series three, she described anti-corruption as “a double-edged sword”, claiming AC-12 only needed to find “enough bent coppers to avoid accusations of a cover up, but not so many that the public starts to wonder if the police can be trusted”, meaning she could be open to turning a blind eye to some bent officers’ activities
  • When contacting the OCG, H is listed as USER 2972. If you put those alphabetise those numbers, you get ‘BIG B’ - could this be a code for BIGgeloe? It should also be noted that the door to Terry’s flat (where Jackie Laverty’s body is still in the freezer) had “Big B” written on it
  • When Fleming was recording The Caddy’s dying declaration, she went through the alphabet and asked him to blink twice on the letter of the top corrupt officer’s name. While she took it to be H, could it have been G, which proceeds it in the alphabet?

Likelihood: As you can see, there isn’t much concrete evidence to back up this theory as yet, which is exactly why it could be true. Jed Mercurio is a big fan of a curveball, and the fact Biggeloe has made a sudden reappearance this series is surely significant. Not to mention the fact she is also currently the bookies’ favourite to be unveiled as H...

THEORY 3: Hastings is being set up as H

Like us, there are many who firmly believe Hastings isn’t H, but is about to take the fall for it, following a number of poor personal decisions that will come back to haunt him.


What people are saying:


  • His financial problems are known about by the likes of Biggeloe, Moffatt, Corbett and the rest of AC-12
  • He’s received a huge payment from Moffatt as compensation for his dodgy investment into the Kettle Bell Complex, the timing of which will not look good following the Eastfield Depot raid
  • He has developed a personal relationship with Biggeloe, who quite frankly, we don’t trust as far as we could throw her

Likelihood: If we were the betting type, we’d place money on Biggeloe and Moffatt being in cahoots to fit our poor fella Ted up.

Since returning, we’ve seen Biggeloe manipulating Hastings, making out like she wants to bring him down one minute and then jumping his bones the next, which makes us immediately wary. We’re also convinced there was another reason she wanted to get into his hotel room - either to plant evidence against him (we haven’t forgotten she was alone in his bathroom before they hooked up), or to capture his semen for the OCG to use against him.

But we also believe she could be conspiring with the shifty Moffatt, who was reintroduced after acting as Roz Huntley’s case officer in series four.

This series has seen him attempting to ‘help’ a broke Hastings get compensation for a dodgy investment in a property scheme, but we have serious concerns about how genuine the Kettle Bell Complex was to begin with. There’s been suggestions Moffatt handing Hastings cash has come shortly before he’ll be arrested on suspicion of being ‘H’, and when he then tries to explain the Kettle Bell complex, it will turn out it doesn’t exist. Sounds very plausible.

THEORY 4: Hastings has a Northern Irish connection to Corbett

Have Hastings and Corbett got previous? That’s the conclusion many have come to after the truth about Corbett’s birth in Belfast and subsequent adoption were revealed.

Some have suggested Corbett is seeking revenge on Hastings for something that happened in his past, hence his attack on Roisin. The most popular theory states that Corbett holds Hastings responsible for the death of his birth father, Antony McGillis.


What people are saying:


  • Corbett and Hastings are both Northern Irish by birth
  • As revealed in series one, Hastings previously served in the Royal Ulster Constabulary, where his friend was killed by a pipe bomb laid by loyalist paramilitaries during a job they were on together. The log book on the incident later went missing...
  • During his attack on Roisin Hastings, Corbett gave her a pattern of injuries consistent with the paramilitary

Likelihood: We’re 100% sold on this theory, as we’ve always thought Corbett seemed to know a lot about Hastings for someone who had never worked for him before.

We’d say Corbett’s father was Hastings’ mate killed in the RUC, and that Corbett believes Hastings covered up his death, because obviously there was no log book of the incident.

With Corbett out to avenge his father’s death, his original plan might have been to frame Hastings as H, but not getting anywhere fast, he could have decided to beat up Roisin as another way to get to Hastings. Her pattern of injuries also suggest Corbett wanted Hastings to feel the effects of a loyalist paramilitary attack, in the same way his father did.

Let’s also not forget that Corbett was also doctoring the AC-12 badges he used to pose as Arnott before the DS had gone against their arrangement, meaning his plans to attack Roisin likely pre-dated Arnott’s betrayal.

THEORY 5: McQueen is working undercover

Many people believe that John Corbett was not the only undercover operative (UCO) embedded in the OCG. Some think McQueen is working for Hastings on a secret over-arching investigation.


What people are saying:


  • She had emotional reactions to the deaths of Maneet Bindra and John Corbett, which revealed that she is not as tough as she makes out
  • She is the only person who has access to the laptop used to communicate with ‘H’ (who Hastings could be posing as)
  • Hastings has been seen seemingly making phonecalls to McQueen
  • Hastings was seemingly the man who paid McQueen a visit at the OCG’s brothel

Likelihood: We spent the whole of the first episode believing McQueen was the UCO embedded in the OCG until Corbett was revealed as the one working undercover. While those suspicions mostly disappeared in episodes two and three, we were forced to reconsider them once again in light of her reaction to Corbett’s murder. And then when you think about it, she does have possible links to Hastings too. But - as we’ve said before - we don’t believe he is H, so those links have to be explained some other way, and her working as a plant would make total sense.

However, actor Rochenda Sandall has teased that all of the theories she’s come across in relation to her character - including this one - are “wrong”.

Speaking on BBC Breakfast earlier this week, she said: “It’s great reading all the theories, I must have spent two hours on Sunday night reading them after the big scene. They’re ALL wrong.”

So should we dismiss the theory she is a UCO, or believe she is trying to trow everyone off the scent? We’d say the latter.

THEORY 6: McQueen is the secret daughter of Jackie Laverty and Tony Gates

As well as being a UCO, people have other theories about McQueen, a popular one being she was the adopted love child of DCI Tony Gates and OCG cooperative Jackie Laverty from series one.


What people are saying:


  • We already know McQueen was adopted, as this was shown in her records that Arnott looked at in episode three
  • Prior to their affair in series one, Laverty and Gates dated back in the 90s. If Laverty had a child during their relationship that she later adopted, it would be around McQueen’s age

Likelihood: Hmm, if we’re being really honest, we can’t really see what purpose this outcome would serve to the story, other than being a nice little Easter egg for fans who’ve watched the show from the beginning. We’d say there’s probably more in the fact that both McQueen and Corbett were adopted.

However, if it is true that McQueen is Gates and Laverty’s daughter, we’d say she almost certainly doesn’t know about it, as she surely would not have been able to stay pokerfaced at seeing her mother’s body in the freezer at Terry’s flat.

THEORY 7: Kate Fleming is H

We warned you there were some curveballs among the theories currently swirling online, and this is the biggest one of them all - that AC-12 favourite Kate Fleming is actually the bent high ranking officer pulling the strings of the OCG.


What people are saying:


  • She was the one who recorded The Caddy’s dying declaration, and therefore would have had opportunity to manipulate it
  • She has been trying to pin blame on Hastings for being H

Likelihood: Admittedly, her sudden promotion from DS to DI has raised some eyebrows among fans (especially as it has so far gone unexplained), but that’s not a reason to suspect her, right?

Funnily enough though, actor Vicky McClure addressed the possibility during the series press launch last month.

“Someone has suggested Kate ‘Helen’ Fleming,” she said, pointing out the famous author, Helen Fleming. “Just throwing in a middle name without me even knowing anything! I’m just keeping my mouth shut.”

However, we just outright refuse to even consider this as an option. Kate is one of the good guys. Surely?

Line Of Duty continues on Sunday at 9pm on BBC One, with episodes also available to stream on BBC iPlayer.