Jed Mercurio has revealed that he wrote in a major clue that Ian Buckells was H back in Line Of Duty's first ever season.
The series creator, 55, detailed how he dropped a sign the officer (Nigel Boyle) was bent back in 2012 after he allowed the caddy Dot Cottan (Craig Parkinson) to speak with criminal Tommy Hunter (Brian McCardie) alone in the back of a van.
And explaining why he made bumbling Buckells the fourth man, much to the shock of many of the 12.8m fans watching the series six finale on Sunday, Jed explained that it was 'really important' that H ended up being someone involved from the start.
So clever: Jed Mercurio has revealed that he wrote in a major clue that Ian Buckells (played by actor Nigel Boyle, pictured) was H back in Line Of Duty's first ever seasonInsurance Loans Mortgage Attorney Credit Lawyer
Jed told the Obsessed With Line of Duty podcast: 'It was always really important to me that it was someone who had been in season one, someone who had been there the whole time.
'We did introduce some characters late, so Thurwell came in late, we went back to Fairbank, who’d appeared in season three, we had the Chief Constable, who had obviously been there since season one.
'But then I don’t think he would have been a satisfying candidate because he had been absent for so long, it would feel like we’d just brought him back in to pin it on him.'
Jed then revealed the clue he'd written into the script, which should have tipped eagle-eyed fans off about Buckells right from the offset.
Sketchy: The series creator, 55, detailed how he dropped a sign the officer (pictured in series one) was bent back in 2012 after he allowed Dot Cottan to speak with Tommy Hunter alone
Corrupt: At the end of series one Cottan (left) and Hunter (right) are seen talking alone, with the officer telling the criminal to play along with the investigation to get immunity
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.'Insurance Loans Mortgage Attorney Credit Lawyer
Jed continued that Buckells being seen as a bit useless and bumbling ended up being written into the script to the officer's advantage.
According to Entertainment Daily, he said: 'So you think he’s just a bit rubbish and so he doesn’t care. And that ended up being part of the evolution of the character..'
Series one of Line Of Duty saw AC-12 investigate DCI Tony Gates (Lennie James) and Jackie Laverty (Gina McKee) is also introduced, with her becoming a key character in following seasons as her body is stored in Terry Boyle's fridge.
Back at the start: The 2021 series of Line Of Duty saw AC-12 investigate DCI Tony Gates (Lennie James) and Jackie Laverty (Gina McKee) is also introduced
Storyline: A series 4 return saw him involved in the storyline starring Thandiwe Newton as Roz Huntley as main corrupt officer
And as H was finally revealed on Sunday night's long-awaited Line Of Duty finale, many shocked fans realised they'd been looking at the mastermind the entire time.
As eagle-eyed fans learned that Superintendent Buckells was the famous fourth man, having liased with the OCG to bring down officers who failed to do their bidding, more clues from past seasons of the show came to light.
Now that it has been revealed, clues from past seasons have been exposed, including bad spelling, a repeated catchphrase and even a hint from Nigel Boyle - the man behind Buckells - as a warning that he was 'one to watch'.
'It was really about the heritage of the series': Jed explained that it was 'really important' to him that the fourth man ended up being someone who'd been in the show from the start
Mugging them off
A very telling yet subtle clue came back in 2017 when Buckells seemed to first reveal his vendetta against AC-12, when he first used the word mug.
During a grilling in series four, Buckells locked horns with Ted Hastings, played by Adrian Dunbar, and stated: 'You lot treat everyone like mugs. Who's the mug now?'
Familiar: A quote used by Buckells in series four reemerged in Sunday's finale
Fast forward five years and on Sunday night's big reveal, at the conclusion of his interrogation, Buckells stated: 'I'm a blundering fool? I'm only the one who's made total mugs out of you lot'- harking back to his original quip.
In typical Hastings style, he hit back just as hard, as he simply stated: 'No-one makes mugs of AC-12'.
The original 'mug line' came when Buckells appeared as a replacement for Thandiwe Newton's character DCI Roz Huntley when she was removed as Operation Trapdoor head.
The Fourth Man-to-be saw Vicky McClure's DS Kate Fleming on the squad, having encountered her in his first in the first season, where he worked out that she was working undercover for the anti-corruption squad.
When Ted learned he had clocked Kate, he covertly met with the villain to instruct him not to blow her cover - something her agreed to with clear chagrin and even refused to help further their investigation as he was 'no grass'.
Could it be? Fans were convinced that the 'H' pattern in Steph's tiles in an earlier episode was a link to the man AC-12 have been hunting for the past six series
When Kate was uncovered, he remained insistent that he did not blow her cover but also made it very clear he had nothing but dislike for AC-12.
Ted then had a heated exchange with Buckells, who was dismissed - not before sneering his now iconic line: 'You lot treat everyone like mugs. Who's the mug now?'
Another mug-based red herring came when fans were convinced earlier this month that home decor - tying in with the mug detail - was the answer to H's identity.
The theory involved John Corbett's widow Steph, when fans noticed an intricate 'clue' hidden in her kitchen tiles. Fans were convinced that the 'H' pattern in Steph's tiles was a link to the man AC-12 have been hunting for the past six series.
And while some dismissed the speculation as wild, it seems it was in fact a true illustration due to the presence of the poignant 'mug' line.
The trio finally found their man - but had he been in plain sight all along?
The mistake that DEFINATELY gave him away
The biggest giveaway for Buckells turned out to be the word 'definately', with his repeated spelling gaffe turning fingers his way.
When Ted and his team saw exchanges between the OCG and Jo Davidson featuring the word misspelt on a number of occasions, he demanded the archives were sifted through in the hunt of the mistake again.
The trawl then revealed the same error in 2019, in communications between the OCG and Lisa McQueen, in the same year in Operation Lighthouse and again in the Lawerence Christopher inquiry in 2003.
This quickly left fingers firmly pointed towards Buckells.
A reveal: The biggest giveaway for Buckells turned out to be the word 'definately', with his repeated spelling gaffe turning fingers his way
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