Some massive Line Of Duty spoilers were hiding in plain sight as the hit drama returned on Sunday night – not that you will have spotted them. 

BBC bosses planted a series of clues on one of the show’s props that were only discoverable with a QR scanner. 

The series six launch saw AC-12 embark on examining MIT boss DCI Joanne Davidson, after she raised suspicions with her conduct during the investigation of journalist Gail Vella’s murder. 

As the scenes unfolded, viewers saw a magazine cover profiling Vella among the clippings found in suspect Terry Boyle’s flat. 

But the cover featured a scannable QR code that revealed clues of what’s to come on the show. 

Twitter user Eddie Davies (@eddaball79) was among those who first noticed that if you open your iPhone camera and place it near enough to the QR code, it will bring up a link that takes you to a letter to DCC Andrea Wise from Chief Constable Philip Osborne.

In it, he raises concerns about how AC-12 and how it is being led. 

“I think it is high time we had a much closer look at AC-12,” he writes. “I’m beginning to question whether this department is fit for purpose especially under its current – and let’s be frank – extremely difficult leadership.”

Osborne lays out concerns about Superintendent Ted Hastings, asking if AC-12 should be “led by someone who himself has been accused of corruption?”

“Is it time for a leadership change?” he asks. “What role should Ted Hastings have in the organisation – if any at all?”

This plot was hinted at in the series launch, as viewers saw DCC Wise and her colleagues arrive at AC-12 HQ for a meeting – much to Hastings’ surprise, as he had not been invited to attend. 

We have also seen Hastings looking to be at breaking point in the series trailer, which debuted earlier this month, suggesting he could be on his way out.

However, this letter not the only hidden nugget for fans to discover – there’s also a clue within the clue!

In the sentence “the question is what we should do next”, the word “next” will be clickable on your phone, and takes you to one of DS Steve Arnott’s medical prescriptions. 

We know Arnott is still self-medicating after sustaining serious injuries in series four, where he was pushed down the stairs by “balaclava man” at the instruction of corrupt solicitor Jimmy Lakewell.  

The prescription lists the medication he is taking, warning that the charzepam he’s on could cause addiction. 

Does this indicate Arnott is in line to succeed Hastings? Or does this mean Arnott’s addiction issues are about to affect his work and will be discovered?

You’ll notice that two-thirds of the way down the prescription, there is some Morse code. 

This then takes you to a TV news report Gail Vella presented as DCC Wise and Commissioner Rohan Sindwhani gave a statement about the conclusion of Operation Pear Tree – the investigation into police corruption that was being led by undercover operative DS John Corbett in series five. 

“Some will wonder why this news is being announced over a holiday weekend,” she questions. “Some might conclude the Police and Crime Commissioner would prefer his statement isn’t examined too closely.

“Perhaps Mr Sindwhani has learned that the secret to high office isn’t to reside in revealing the deepest truths, but in telling the most attractive lies…”

Was this report what ultimately led to Vella’s murder? 

Line Of Duty fans will know that the last time we saw Morse code used on the show, it was by DI Matthew ‘Dot’ Cottan in previously unseen footage from his dying declaration. 

It revealed that the mysterious “H”, who was believed to be the boss of the organised crime group, was not actually one person, but a clue pointing to four corrupt senior officers in league with the OCG. 

So far, three of them have been revealed – Cottan, ACC Derek Hilton and legal counsel Gill Biggeloe, with the other still to be found.

The first episode of series six also had some serious links to the very first season, with the return of Terry Boyle – a vulnerable man who previously exploited by the OCG who has now been arrested for Vella’s murder. 

There were also allusions to DCI Gates’ former lover Jackie Laverty, who the OCG killed and had been storing parts of her body in a freezer in Boyle’s flat.

Line Of Duty continues on Sunday at 9pm on BBC One.