Warning: contains spoilers for Line Of Duty series one, two, three and four (until episode four). And some wild speculation.

“How do you know when an executive officer is telling lies? His lips move.” So said SI Ted Hastings reporting back after lunching with ACC Hilton in Line Of Duty series four episode one. It was a characteristically wry comment from Hastings, a character who brooks no truck with bent coppers and PR-manipulators like Hilton. Was it, though, more than that? Was Ted calling Hilton a liar a crucial clue as to what’s really been going on in this series?

After the story of Matthew ‘Dot’ Cottan, aka The Caddy, and the connective thread between the last three series, was resolved in explosive form in last year’s finale, Line Of Duty series four appeared to have moved on to pastures new. Dot hasn’t been spoken of since he bled out on that housing estate verge, providing DS Fleming with a final testimony that named names as he did so.

In the series four opener, we met a brand new suspect for AC-12 in Thandie Newton’s DCI Roz Huntley, and a new whodunnit mystery in ‘who is Balaclava Man?’, the murderer who killed Baswinder Kaur and Leonie Collersdale, and whom it’s assumed attempted to abduct Hana Reznikova. Goodbye Tommy Hunter, Dot, Nigel Morton, Lindsay Denton and all that history, this series is a fresh start, it all seemed to say.