Line of Duty's big typo twist: What is the significance of "definately"?

In the fifth episode of bent copper nail-biter Line Of Duty - while we were still reeling from the shock revelation that Acting DSU Jo Davidson (Kelly Macdonald) was a blood relative of gangster Tommy Hunter (with high "runs of homozygosity" between the two, at that) - Davidson hopped on her laptop and fired up that mysterious messaging app to check in with her “Unknown” handler.

After the “Fourth Man” (or woman - let’s not be sexist dinosaurs like dear old Ted Hastings) expressed anger that two OCG thugs were killed during AC-12’s raid on the gun workshop, he or she chillingly ordered Davidson to “get rid of” DI Kate Fleming (Vicky McClure).

Davidson, who clearly wants to leave her duplicitous double life behind and stop having to lock her flat door quite so thoroughly, replied: “As long as it’s my last job.” “Definately” came the response. Hang on, murmured a nation of armchair detectives. Haven’t we’ve seen this spelling mistake somewhere before?

Well spotted, fellas and wee girls. It was also a crucial clue during the last series. So what might this spot of grammatical chicanery from writer Jed Mercurio mean?

In series five, the faceless criminal mastermind known as “H” exchanged online messages with undercover cop John Corbett (Stephen Graham) and his partner-in-shadyness Lisa McQueen (Rochenda Sandall) at their Kingsgate Printing Services lair. When Corbett suggested an armed raid on the heavily fortified Eastfield Depot, “Unknown” warned the gang that the heist was “definately high risk”.

Def-the-what-now? Was this a genuine mistake from the hit BBC One production or a deliberate clue? As any fule kno, Mercurio is a devil for detail and includes nothing by accident. It “definately” had to be on purpose. Especially when AC-12 boss Supt Hastings (Adrian Dunbar) was promptly seen slamming shut a laptop in his Edge Park Hotel room and later disposing of it.

Mother of God, surely Hastings wasn’t the corrupt senior cop in league with the crime syndicate? Those of us in denial about Hastings’ possible guilt reassured ourselves that he’d never make such a glaring blunder. The gaffer is so by-the-book, we protested, he surely spells correctly to the letter. The very letter.

Besides, it’s an easy mistake-ah to make-ah. According to the Oxford Dictionary, “definately” is one of the top 10 most misspelled words in the English language - alongside the likes of “recieve” (receive), “seperate” (separate), “pharoah” (pharaoh) and “accomodate” (accommodate). It's like the questions in a fiendish school spelling test.

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In the next episode, AC-12’s resident cybercrime expert Amanda Yao (cult heroine Rosa Escoda) managed to access the mobile metadata from H - his IP address was located in Spain but could have been re-routed from anywhere - and, impersonating the unknown user, made online contact with the OCG (now based in the back office of seedy Flicker nightclub).

Impatient with Yao’s reliance on a nerdy flowchart of “prepared responses”, Hastings took over communication with Corbett, posing as H, and proposed getting the stolen Eastfield Depot goods out of the country.

When Hastings typed “I can definately pull the right strings”, alarm bells clanged. It was the exact same misspelling as the real H. Had the diesel-sucking head honcho inadvertently given himself away with a schoolboy spelling error?

Viewers took to social media to triumphantly claim the typo was indisputable proof that Hastings was H. However, actor Martin Compston (who plays waistcoat warrior Steve Arnott) waved such theories aside by joking that co-star Dunbar was "definately a wee gobs***te”.

By the nerve-shredding 90-minute series finale, Hastings was suspended from duty and under heavy suspicion. Even his magnificent hair was looking less glossy than usual. Would the spelling mistake, like that cash-stuffed envelope in his hotel room, prove another nail in his corrupt coffin?

While being grilled by AC-3’s DCS Patricia Carmichael (the brilliantly supercilious Anna Maxwell-Martin) for allegedly plotting to kill Corbett, Ted said it had all been part of his unauthorised undercover mission. He claimed to have closely studied the spelling habits of H and cunningly copied them.

As Carmichael said sceptically: ”You’re the SIO (senior investigating officer) on one of the biggest anti-corruption operations this force has ever seen and you have the headspace to learn to spell like H?” “Yes,” growled Hastings.

Carmichael was unconvinced: “Isn’t it more likely that you inadvertently misspelled this word? Isn’t it more likely that you made the same mistake as H because you are H?” “I am not H,” insisted Ted, his hair losing a little more of its lustre.

In a typically twisting interview scene, the tables were turned and the rotten apple was instead identified as pouting police lawyer Gill Biggeloe (Polly Walker). SuperTed received a slap on the wrist but was seemingly in the clear. The nation breathed a sizeable sigh of relief.

Well, until now and the resurfacing of that “definately” slip-up. Does it indicate that Hastings was “H” after all and is now controlling dodgy Davidson? Surely he wouldn’t order the killing of longtime sidekick Kate? Or is it all just another “Ted herring” and the typo-prone puppetmaster is the same “Fourth Man” as before - a "big bad" yet to be unmasked?

Either way, it’s surely “definate” confirmation that Davidson is colluding with the same shadowy top dog who has been a thorn in AC-12’s side all along. And that top dog needs to switch on autocorrect in their computer settings before they embarrass themselves any more.

Still, spelling purists should be grateful for small mercies. At least “definately” isn’t as cringe-inducing as those saucy texts between hapless DSU Buckells and witness Deborah Devereux which were discovered last week. "Will u show me your trunshon?" indeed.

Line of Duty continues on Sundays on BBC One. Read our Line of Duty episode 5 recap, and our theories on who got shot in Line of Duty. Check out the rest of our Drama coverage, or take a look at what else is on this week with our TV Guide.