Warning! This article contains Line Of Duty spoilers of the highest order. 

It’s been over a week now since Line Of Duty’s divisive series finale, which finally revealed DSU Ian Buckells as the mysterious “H”. 

Many fans are still struggling to understand quite how the incompetent copper came to be unmasked as the so-called “fourth man”, despite repeated explanations from actor Nigel Boyle and the show’s writer Jed Mercurio. 

“We’d been directing the audience towards a particular image of the kind of character that ‘H’ would be, that ‘H’ would be a criminal mastermind, and we wanted to make different commentary on the way in which someone can do a lot of harm without necessarily being a mastermind,” Jed said recently on the Obsessed With Line Of Duty podcast.

“You think [Buckells] is just a bit rubbish and so he doesn’t care. And that ended up being part of the evolution of the character.”

“When he reveals his story, it’s the fact that his personal standards were low, that he wasn’t committed to honesty and integrity, and that then made him someone who was vulnerable to being groomed by the OCG into being a fixer for them,” Jed added.

Sure enough, if you look back over the six series, there were plenty of clues about Buckells’ corruption hidden in plain sight all along. Here are just six of them… 

His appearance at Edge Park Golf Course

Buckells made his debut appearance back in Line Of Duty’s first series, when he was a DI in the Tactical Operations Division. 

While he featured in a number of scenes, it was one particular blink-and-you’ll-miss-it moment that proved to be the most significant. 

When DCI Tony Gates went to apprehend OCG leader Tommy Hunter at Edge Park Golf Course, Buckells could momentarily be seen arriving there.

You might’ve had to slow down the speed to actually spot him in the car park, but this proves how he’d been an associate of Hunter’s the whole time. 

The golf clubs

Golf was hugely symbolic in Line Of Duty, as not only did Tommy Hunter play, but the sport was how he recruited DI Matthew “Dot” Cottan into the OCG, as Cottan worked as his caddy as a child before going on to embed himself into the police force.

Therefore, we probably should have paid a lot more attention to Buckells’ love for golf in the most recent series.

A set of clubs was frequently seen in the corner of his office, while some were also pictured in the boot of his car after DCI Jo Davidson planted the missing Gail Vella files in his vehicle.

A painting of a golfer could also be seen hanging in his office. 

His relationship with ACC Hilton

Buckells was a favoured officer by Derek Hilton, having twice been installed onto cases with OCG connections at the bent copper’s request.

He was appointed by the then-Chief Superintendent as the senior investigating officer of Jackie Laverty’s disappearance in series one, after she was murdered by the OCG. 

Hilton then brought Buckells in to replace DCI Roz Huntley on Operation Trapdoor in series four, which investigated the kidnapping and murder of Baswinder Kaur, the disappearance of Leonie Collersdale and the attempted kidnapping of Hana Reznikova.

This series conclusion revealed how Hilton had been involved in helping to cover up a scheme whereby the OCG would kill victims and cover them in the DNA of coppers to bribe them into colluding in their criminal activities. 

Therefore, it was likely Hilton installed Buckells on both these cases to help him in the conspiracy.

His history with Ryan Pilkington

Ryan Pilkington ended up being arguably the biggest baddie of season six, but he and Buckells had history prior to him joining MIT. 

Pilkington was arrested in series one after colluding in the kidnap of DS Steve Arnott, and after being questioned by DC Fleming, he was then interviewed by Buckells, who let the teenager off without any charges. 

This meant Pilkington did not obtain a criminal record that linked him to the OCG, and meant he was later able to pass background checks and join the police as their inside man in series six. 

It was also revealed that Buckells was instrumental in hiring Pilkington onto the Murder Investigation Team, with Davidson revealing he’d told her he was a family friend. 

The Hunter/Caddy chat

There was a huge clue about Buckells’ corruption back in series one, when he allowed The Caddy (aka DI “Dot” Cottan) to speak with Tommy Hunter alone in the back of a police van, following his arrest. 

Line Of Duty’s creator and writer Jed Mercurio addressed this in a recent BBC podcast, where he explained how “H” had to be someone who’d been involved in the show from the start.

He said: “It was really about the heritage of the series, going all the way back to season one, where Dot Cottan says, ‘Oh, can I just have a quick word with Tommy Hunter in the back of the van?’ and Buckells goes, ‘Yeah, alright’. OK, like, really, is that what you should be doing? Of course, not.”

His previous clash with AC-12

Admittedly, there don’t seem to be many officers in Central Police who are big fans of AC-12, but Buckells was less than thrilled to see Fleming working undercover on his team in series four, repeatedly threatening to blow her cover. 

He would withhold information about Operation Trapdoor from her, insisting he was “no grass for AC-12”.

After eventually blowing Fleming’s cover – something he denied during an AC-12 interview – his actions temporarily rendered all of AC-12’s efforts to pursue DCI Roz Huntley redundant, thus keeping the innocent Michael Farmer in the frame as “balaclava man”.

Line Of Duty series 1-6 are available to stream on BBC iPlayer.