Line of Duty ending explained – how season six revealed the identity of H, and all the important details from the finale

And when we finally – finally – got to see who was sitting on the other side of the table in AC-12's interrogation room it was... Buckells. Bloody Buckells! (If you listened carefully at 9:34pm, you probably heard a howl of disbelief as millions of Line of Duty fans across the country yelled at their TV sets. Mother of God!)

"All the time we were here, thinking we were chasing some criminal mastermind, but no," Superintendent Ted Hastings (Adrian Dunbar) said, fuming: "Your corruption was mistaken for incompetence."

So, that's that. Line of Duty is done and dusted for 2021. But there was quite a lot to absorb in that final episode – so here's the season six ending, recapped and explained.

DCI Ian Buckells revealed as H, the "Fourth Man"

After all that, DCI Ian Buckells (Nigel Boyle) was the big bad! But maybe a bit less "big" than everyone anticipated. "Yeah right, I'm a blundering fool. I'm only the one who's made total mugs out of you lot," he said.

In 2003, when Buckells was only a Detective Constable, he was working on a corrupt team of cops who mishandled the Lawrence Christopher case on the orders of Tommy Hunter, ensuring that the OCG boss's son Darren Hunter escaped justice. At the time, it was Buckells' boss Marcus Thurwell (James Nesbitt) who was the criminal cop, although (suspiciously) future Chief Constable Philip Osborne (Owen Teale) was also involved in the case.

After the events of 2003, Buckells then "failed upwards", as Hastings put it – somehow climbing the ranks, despite his mediocrity. Even after Tommy Hunter was killed in 2014 and the OCG dissolved into multiple smaller OCGs, Buckells kept tipping off the criminals and bent coppers. He'd send them details and instructions via an encrypted messaging service, with Thurwell handily assisting from his retirement home in Spain by routing the messages through his Spanish IP address and then back to the UK again. His motive? Greed. "As you made your way up through the ranks, there wasn't anything that you wouldn't turn your hand to as long as the price was right," said Ted. "That's the top and bottom of it, isn't it, fella?"

In Buckells' mind, he was just giving the criminals information and letting them be the ones to make the decisions and do the killings. "That's the OCGs! That's their doing! I just pass things on. I didn't plan it or nothing, did I?" All he did was collect the money and use it to pay for swanky houses, and he sees nothing wrong with that.

And where does Jo Davidson fit in? Well, Jo simply didn't know it was Buckells calling the shots! She was sitting in an office right next to him, and she thought Buckells was just an incompetent fool who she could frame for her own bent-copper actions. Which she managed, quite successfully at first – to Buckells' profound bafflement.

All the time when Jo was talking to "H" on her special laptop throughout season six, she thought she was talking to Patrick Fairbank (George Costigan) – even though she was actually talking to Buckells. That's because Tommy Hunter told teenaged Jo a horrible, useful lie: he claimed that the man who raped and impregnated Jo's mother Samantha Davidson was none other than Fairbank. Samantha Davidson had recently died, so she wasn't around to contradict Tommy. Jo believed this lie up until the moment AC-12 broke the horrible news to her that Tommy was not just her uncle, but her real biological father.

The Fairbank's-your-dad lie must have been part of Tommy's strategy to control and coerce his niece/daughter Jo as he pushed her into the police force in the late 1990s. Back then, Fairbank was a senior corrupt cop (and serial child abuser), and he was likely the one passing on orders to more junior cops in that clandestine network of bent coppers. But even after Fairbank retired, and even after his arrest and conviction, Jo continued to believe that her rapist father was calling the shots – first from home, and then from prison.

So when she finally told AC-12 about Fairbank, she thought she was giving them "H" – and AC-12 thought so too. But a search of Fairbank's cell revealed absolutely no communication equipment, and in his interrogation Fairbank was utterly baffled (though a lot of that was surely due to Alzheimers / memory loss). "I've not the foggiest!" Fairbank said.

Then DC Chloe Bishop (Shalom Brune-Franklin) came to the rescue! Line of Duty fans have been suspicious of AC-12's brainy new recruit ever since she appeared this season, but in the end it was entirely unwarranted.

Chloe did the desk research and delivered the goods. By searching through all the old case files for the Lawrence Christopher case and newly-found ones from Operation Lighthouse, she found handwritten notes from Buckells – in which he spelled "definitely" as "definately", just like the person communicating with Jo and the OCGs. Got him! "Definately" wasn't a red herring – it was the vital clue all along.

AC-12 then collected more evidence against Buckells, and brought him in for questioning. Facing him across the table were Steve, Ted, and Kate (presumably on loan from Operation Lighthouse), while Patricia Carmichael opted out – in favour of lurking in her office doorway, observing the interrogation in a socially-distanced manner.

The evidence was overwhelming. In an interrogation peppered by "no comment"s from Buckells, the AC-12 trio revealed the fingerprint-covered laptop that had been found hidden in his cell at Blackthorn Prison; the IP addresses that matched the one at Thurwell's in Spain; and the analysis of the "definately" misspelling.

They had messages suggesting he'd masterminded the attempted abduction and murder of both Jo and DI Kate Fleming (Vicky McClure). They had evidence of his £3 million property portfolio, far beyond what he should realistically be able to afford. And in one of the houses, they'd found a DNA and fingerprint-covered hard drive with evidence of him approving the 2019 Eastfield Depot raid.

Faced with the evidence, Buckells saw he couldn't keep on saying "no comment". But he had another plan in mind. "So you see the thing is, DCS Carmichael is meant to be taking over, in't she? But she ain't in here. So that makes me wonder if she doesn't want to be associated with detecting institutionalised corruption. Because officially institutionalised corruption don't exist, does it? Officially, 'H' or the Fourth Man or whatever you want to call him, he don't exist neither. So that makes me realise that everyone would be much happier if this all just went away. So I'll take immunity and witness protection, thank you very much."

So Buckells began to spill the beans. According to him there was no set group of four "H"-es running the shop, so the theory about Dot's dying declaration seems to have been a bit shoddy.

Instead, Tommy Hunter was the top man in this whole thing; after his death, the OCG split into multiple, smaller OCGs. Back then, Buckells was just a junior guy "passing on orders". The senior figures used to be Fairbank and Thurwell; then they were Derek Hilton (Paul Higgins) and Dot Cottan (Craig Parkinson); then the mantle fell to Buckells. he made no mention of Gill Biggeloe, who AC-12 previously had down as an 'H'.

But then Buckells' plan to seek witness protection or immunity hit a rock he had not anticipated – and the cockiness started to ebb away. The trick up AC-12's sleeve was a question about whether he and/or Chief Constable Osborne conspired in the murder of Gail Vella. Because, in this particular instance, Buckells and/or Osborne weren't just going along with OCG plans, but actually ordered the killing. Buckells had found out via Lee Banks that Gail was digging into the Lawrence Christopher inquiry, and he needed her to stop before she got to the truth.

"Naturally, you're aware failing to cooperate with this inquiry would make you ineligible for witness protection," warned Steve, while Kate piped up with: "And you're also aware that confession to conspiracy to murder would make you ineligible for immunity from prosecution."

Trapped! "No one makes mugs of AC-12," said Ted, sending Buckells back to prison, where he remains. But – as we learned at the very end – Central Police has submitted an application for public-interest immunity in legal proceedings against Buckells. If successful, no evidence relating to institutionalised corruption will be heard in court; Buckells' plan may work out after all.

Got it? OK, now we've got that sorted, let's talk about what else happened in the episode:

The OCG strongbox under the floor

When beardy Lewis and that other bloke from the OCG turned up at the gun workshop on Ryan's tip-off, what they were really meant to be doing was tearing up the concrete floor and removing the OCG's strongbox. But the police got there first, and shot them both dead. Then, when Kate had the bright idea of using radar to look underground, she struck gold: a box full of OCG goodies.

We've seen before that OCG bosses like to hoard incriminating evidence, so bent coppers and thugs alike are forced to continue complying. From this box, DS Chris Lomax (Perry Fitzpatrick) recovered the OCG's blackmail material on Ryan Pilkington (a knife he used to kill PC Maneet Bindra) and Carl Banks (the gun he used to kill Gail Vella, and the gloves he wore). That said, not all of this could be taken at face value: the knife covered with Jackie Laverty's blood was, as Steve handily already knew, put in Tony Gates's hand against his will – specifically to create this evidence.

The prison officers kidnapped Jo to kill her

Ah, Leland and Merchant, Line of Duty's most evil double act. The prison officers from Brentiss Prison are in the pocket of the OCG, and in this episode they were given orders to kill prisoner Jo Davidson ("JD definately high risk. Contact assets in BP"). As Jo was on the Vulnerable Prisoner Unit, with security cameras everywhere and "elevated monitoring", they couldn't reach her there – so they instead carried out an audacious plan (presumably with plenty of help) to remove her from the jail and put her in a transport van, so the OCG could stage a kidnap.

Someone forged a "production order", calling Jo Davidson in for an interview at Hillside Lane Police Station. It looked pretty legit on the system: they even forged the signatures of DS Chris Lomax and DI Kate Fleming. Leland, Merchant and an accomplice then loaded Jo into the back of a van; the plan was for a bunch of balaclava men to ambush the police transport en route to the Hill, pretending to hold the prison officers at gunpoint. The balaclava men could then kidnap and kill Jo Davidson: problem solved!

But they reckoned without AC-12's Amanda Yao (Rosa Escoda), who had intercepted the encrypted message from "H" to his criminal cronies (thanks, in part, to the seizing of communications equipment at Thurwell's house in Spain). Jo's life was in danger! AC-12 scrambled into action, putting all the pieces together in time to track down the van and get to Jo before the OCG did.

Plus, AC-12 pulled off an even bolder move. In a scene that took place off-screen, Steve and Kate stopped the van and removed prison guard Leland from the back, replacing her with an armed and angry Kate. Steve stepped in as driver, and Merchant was forced to comply with this new set-up from the passenger seat. So when the balaclava men jumped out of their shiny black cars to ambush the van as planned, they were instead surprised by Steve and Kate, followed by a whole load of Armed Firearms Officers who had been waiting in the wings.

This audacious switch-up meant that AC-12 were able to get more balaclava men in custody, and also demonstrate to Jo that she really was about to be killed by "H" – and it was time to give up his identity.

Steve finally went to Occupational Health

Steve managed to accomplish that heroic van ambush with nothing but a taser gun (and a gun he cheekily nicked off one of the balaclava men). That's because he had to surrender his "blue ticket" firearms licence, on the orders of Occupational Health – who finally compelled him to go to an appointment, under threat of suspension from duty.

As the medical counsellor (played by Steve Oram) told Steve, his urine sample had revealed "very high doses" of painkillers. The counsellor noted the serious assault Steve suffered in season four, and raised an eyebrow at Steve's claim he was only taking painkillers for a couple of minor sports injuries. He suggested Steve should take some time off work, and told him he'd have to surrender his firearms licence voluntarily, or risk having it formally removed. In addition, he probed the mental trauma Steve must be carrying from having witnessed so many colleagues' violent deaths.

All very fair. And there was no sense that Steve was being punished; this was more about looking after his welfare, and keeping everyone safe. Steve's now getting treatment and therapy, and so is Kate – having been through quite a lot during the last few years.

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Hastings came clean on John Corbett

Just as Ted Hastings was about to storm off to tell DCS Patricia Carmichael (Anna Maxwell Martin) about Buckells being 'H', Steve and Kate decided it was the right moment to confront the gaffer with what they knew. And it took a bit of beating around the bush for him to come clean – but when he did, the air was finally clear between Line of Duty's famous trio.

First they told him Steve had been in contact with Steph. Ted tried to turn it back around on Steve at that point, saying he'd heard from her about Steve's painkiller addiction and had given him a chance to sort himself out. ("That's loyalty.")

Then they told him what they really knew about Steph, which was that she had a bundle of £50 notes in the attic – given to her by Ted. Ah, said Ted – yes, I did keep half of that bribe money, but at least it went to a good cause. "Are we done?"

Finally, having given Ted a chance to 'fess up to the whole thing off his own back (a chance which Ted didn't take), Steve and Kate revealed what they really knew: that Ted told Lee Banks there was a rat inside the OCG, directly leading to undercover police officer John Corbett's death. At last, Ted was confronted with the truth – and he could deny it no longer.

"I swear to God, I did not disclose John Corbett as a UCO," he said. "I told Lee Banks that there was an informant in the OCG, no more than that. I thought that Corbett, when he heard about it, he would go to ground, he would hand himself in at the nearest police station. It was my way of bringing him in. I swear to God."

Prodded about whether he understood there was a risk of Corbett coming to harm, he said: "Well that is the worst part of it, yes. John Corbett had been involved in the deaths of four police officers, our Maneet being one of them. He had beaten and tortured my own wife, so I thought he had it coming to him in spades. But what I didn't know, was that he was the son of a woman I cared deeply about, many years ago. If there is one thing I could take back, it would be that. What a terrible thing I did. What a terrible thing I did. Giving that money to that young woman was my way of atonement, what little there was of it." Steph doesn't know – "and if she did, what would she make of it? Who's going to judge what I did? Her? The law? My colleagues? God?"

Steve and Kate couldn't quite decide what to do with that information, having interviewed him off the record. But right at the end, Ted did the decent thing himself, and confessed. Well, sort of...

So, having just declared to Carmichael that he intended to fight his own mandatory retirement, Ted left AC-12. But he then returned, with something important to tell Carmichael. To Carmichael's slight bemusement, he declared that he had given Lee Banks the information that led to Corbett's death.

It was a confession, but still quite an ineffectual one. Because Carmichael is not interested in one thing and one thing only (bent coppers!), and she'll have no interest in following this up in case it can benefit her own career in some way. She took no notes, and there was no voice recorder running (to our knowledge). Perhaps it has cleared Ted's conscience a little and removed some of Steve and Kate's unease, but it was quite a wishy-washy way to do it. Plus, he still hasn't told about the £50k off-the-books gift to Steph Corbett.

Jo Davidson in witness protection

By working with AC-12 and identifying Fairbank, Jo Davidson secured herself a spot in witness protection (despite the fact that Fairbank wasn't actually the Fourth Man). And in those closing moments, we got a glimpse of her outrageously idyllic new life. Cosy jumper! Large, rustic cottage! Good-looking girlfriend! Golden retriever! She certainly got a good deal out of her new identity, especially compared to Gill Biggeloe. And despite Jo's previous fears that she'd still be vulnerable to OCG assassination in witness protection, it's so far so good for her personal safety.

A happier ending, too, for Terry Boyle (Tommy Jessop), who has been given a spot in a nice-looking group home alongside other people with Down's Syndrome. He got a friendly welcome from the staff and other residents, and he should now finally be free of criminal exploitation – as an inquiry examines systemic failures to protect his welfare.

And Farida is out of jail and back on active duty at Hillside Lane. Good for her!

Future of AC-12 still in doubt

Buckells might be locked away, and Darren Hunter might be under investigation for the murder of Lawrence Christopher – but it's hardly a triumphant end to season six for AC-12.

Ted is retired, even if he means to contest it; the process to merge and cut back on AC-3, AC-9 and AC-12 is still underway; close colleagues of the Chief Constable have been appointed to senior anti-corruption jobs; Steve must face his addiction and his back problems; Kate wants to rejoin AC-12, but may derail her career if she does; and institutional corruption remains rampant. Across all six seasons, our anti-corruption heroes have been picking rotten apples out of the barrel, but they can never remove enough to stop the rot.

Carmichael's now in the ascendant. When Kate told her about MIT's cold case inquiry into the Lawrence Christopher case, she only said "good luck with that" – and then turned down Steve's request for a parallel inquiry into the serving police officers who were involved in that deliberately-botched case under SIO Thurwell. "Historic corruption cases aren't a priority," she said. She's also told Ted that, despite the deluge of evidence, she's still not prepared to accept this as institutional corruption rather than Ian Buckells acting alone.

And Chief Constable Philip Osborne remains in charge of Central Police, despite his concerted attack on anti-corruption – and AC-12's very legitimate doubts about him. In a televised statement worthy of a super villain, Osborne said: "I give you my personal assurance that any failings in the original inquiry will be thoroughly investigated. Lessons will be learned. Throughout my career, whenever I've encountered wrongdoing, I've acted. But let me be clear: these are the misdeeds of a few rotten apples. And to invoke institutionalised police corruption is an outrageous lie and an insult to my officers. The public don't want police officers to be held to account for every little thing they're meant to have done. They want us to get on with the job, and that's what we will do."

And as all the pictures symbolically came off the AC-12 pin-board and were stowed away in a box, Jed Mercurio gave us one final line: "Currently AC-12's powers to curb wrongdoings in public office have never been weaker." The end!

Want more analysis of the finale? Take a look at these Line of Duty unanswered questions, or check out all the Line of Duty red herrings spotted throughout the series.

Line of Duty season 6 is available on BBC iPlayer now, and we have all the latest news on Line of Duty season 7. Check out the rest of our Drama coverage, or take a look at our TV Guide to find out what else is on.