A police vehicle hijacked. Three officers murdered. Everything points to an inside job. Who you gonna call? 

Step forward AC-12 (the anti-corruption unit, aka bent cop busters). In honour of the show’s fifth run, here are five reasons to get excited.

Why the new season of Line of Duty is going to be its best yet:

1 . You’ll be hooked within the first five minutes. 

No other show grips you by the shoulders and pins you to the sofa quite like Line Of Duty. The series starts with a bang before quickly revealing a Gordian knot of interconnecting threads. By the time DS Arnott’s (Martin Compston) trademark frowny face appears, you’ll be obsessed.

2. The female characters are front and centre

The always-brilliant Vicky McClure returns as DS Fleming, joined by a raft of new female faces including hard-as-nails Lise (Rochenda Sandall) and she’s-hiding- something DSU Powell (Susan Vidler).

3. The twists will keep you on your toes 

Writer Jed Mercurio (Bodyguard) is a master of misdirection. He gives you just enough of a headstart that you think you’ve cracked the puzzle, only to find that you’ve been led down a dark alley and someone has a gun to your head.

4. The interviews are TV gold 

Line Of Duty is renowned for its extended cat-and-mouse interview scenes. As soon as DS Arnott starts scrolling through his iPad, asking people to “direct their attention to document A”, you know you’re in for an unbearably intense few minutes.

5. We might finally find out who the corrupt Mr Big is

Superintendent Hastings (Adrian Dunbar), head of AC-12, has certainly cornered the market in suspicious side-eye from behind a venetian blind. But surely it can’t be him… can it?

So basically, trust no one, clear your Sunday nights and prepare your theories for the office on Monday mornings. You do not want to be the one missing out.

Line Of Duty starts 31 March, 9pm, BBC One

Images: BBC