Hello, I'm new to Line of Duty what can I expect?

I'm setting you some homework. Get yourself onto BBC iPlayer and watch all four series pronto. Clear your diary. It will take 23 hours. See you on the other side.

Wait! Who are the main protagonists?

I'll give you a run through but like Game of Thrones you shouldn't get too attached to any of them. The main ones on your radar should be the AC-12 team.

Is that like the A-Team?

Kind of. But they don't have a black van with a red stripe on the side.

What do they have?

Police things like badges and notebooks. AC-12 is an anti-corruption unit. The boss is Superintendent Ted Hastings (Adrian Dunbar), there's undercover specialist DI Kate Fleming (Vicky McClure) and dogged investigator DS Steve Arnott (Martin Compston), who is also the owner of an impressive waistcoat collection.

Hang on, don't I recognise Martin Compston from somewhere?

Yup, he's the Greenock-born actor who landed his big break in Ken Loach's 2002 film Sweet Sixteen. Compston has gone on to play everything from a cheeky chef in Monarch of the Glen to Lanarkshire serial killer Peter Manuel in the crime drama In Plain Sight.

But he doesn't sound Scottish in Line of Duty?

Indeed. Compston's character speaks with an estuary English twang.

What else do I need to know?

Line of Duty is the brainchild of Jed Mercurio who also created Bodyguard.

The one starring Richard Madden?

The very same.

Is he in it?

Nope. But Line of Duty has had some stellar guest stars including Keeley Hawes, Daniel Mays and Thandie Newton. Look out for Stephen Graham as the murky "balaclava man" in series five.

Is that a spoiler?

Negative. But he isn't the only one sporting knitted headwear.

That sounds intriguing.

It certainly does. Anyway, that's your lot, fella.

But I'm not finished …

[steely gaze] I have the right to be questioned by an officer at least one rank senior.

Line of Duty begins on BBC One, tonight, 9pm