Line of Duty isn't even back on TV yet, but show creator Jed Mercurio already has fans totally puzzled over the new series.

On Thursday (December 19), the writer tweeted the first "plot clue" for series six: a pack of Australian chocolate biscuits Tim Tam.

Yeah, thanks for that, Jed. Really helpful.

Line of Duty creator Jed Mercurio series six plot clue
Jed Mercurio//Twitter

Still, Jed's cryptic post naturally got the fan theories going – and some of them are pretty convincing.

Many realised that the broken-in-half biscuits are made by Arnott's, which is the same surname as investigator Steve Arnott (played by Martin Compston).

So, one person simply guessed: "Arnott breaks."

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Another fan went further: "My theory is the biscuit company is Arnott's and the biscuit bar is breaking so Steve will have broken up with his girlfriend and be investigating her or someone in her department."

Not totally impossible. But a third did even more research, discovering that the maker of the biscuit has the same surname as Steve's colleague Kate Fleming.

They posted: "The guy who created the biscuit is called Timothy 'Tamworth' FLEMING. For a company called ARNOTTS.

"Nothing is a coincidence on this show! BUT WHAT DOES IT MEAN, I think my head is exploding..."

Another added: "Either Steve and Kate get it on or he finds out she's the fourth H!"

kate fleming
Steffan Hill//BBC

So, is Kate actually 'H'? Is Steve about to break? Or are they just going to end up in bed together?

Jed, we're going to need more biscuits.

Although we know very little about series six at the minute, the show did recently cast actress Kelly Macdonald as AC-12's next adversary, while Compston has weighed in on the possibility that Superintendent Ted Hastings could be the ultimate villain.

The sixth series is expected to air before the end of next year.

Line of Duty airs on BBC One. Series 1-5 are available on boxset now.


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Lettermark

Adam Silverstein is a freelance sub-editor and writer at Digital Spy, and he specialises in music, TV and movies.