Am I a Luther convert? Yes. The plot might not stand up, but it's a cut above most cop series

The show's garnered praise for Idris Elba's performance, but really its most important character is London.

Idris Elba.
Monster with a badge: Idris Elba in Luther. Photograph: BBC Pictures.

Luther
BBC1

Not even a TV critic can watch everything, so this, the third series of Luther (Tuesdays, 9pm), is my first. Luckily, it’s pretty easy to catch up. Luther is nothing if not hyped, which is why I’ve known ever since it started in 2010 that DCI John Luther (Idris Elba) is a maverick cop (though in this instance the cliché “maverick” means “borderline nutter” as opposed to someone who isn’t crazy about paperwork).

I was also aware he was involved in some funny business with a brilliant killer played by Ruth Wilson – though she seems to have disappeared this time round. In series three, her character appears only on a noticeboard, where her photograph has been stuck alongside all of Luther’s other “victims” by the coppernow investigating his dubious methods.

Yes, Luther is under investigation and it’s his loyal sidekick DS Justin Ripley (Warren Brown) who’s the mole. I doubt this state of affairs will last – Luther is almost certain to win Ripley round in the end – but it’s fun for now, a pleasing seam of reality making its way into what must be one of the most preposterous shows ever made. Not that I mind. However loopy, Luther is still quite frightening, the kind of programme that makes you worry about walking home from the bus stop (as usual, most of the violence – and there is plenty of it – is directed at young women).

It makes you jump and sometimes (perhaps this is just me) it makes you run out of the room with your hands over your eyes. In the first episode, a killer, having decided that he would not allow the police the satisfaction of taking his fingerprints, went into his kitchen and shoved his hand in his blender – a refreshingly edgy take on the 21st-century craze for juicing.

It’s quite clear that Neil Cross, Luther’s writer, is deeply in love with his creation. His passion is there in the small stuff: a serial killer who dresses his victims up like Siouxsie Sioux (“late-Eighties post-punk”, as Luther explains it to Ripley); a serial killer who fishes in the Thames for freshwater crayfish and then eats them for his tea with a bag of chipshop chips. Why does Luther drive an old Volvo estate? I don’t know but I like that he does. Delightfully at odds with his tendency to dangle suspects by their ankles over the edge of tower-block balconies, its low-slunk bulk is one reason among many why the viewer is never quite sure how to take him. Luther not a loveable rogue; he’s a monster with a badge. And yet he is sometimes on the side of the angels, morally speaking, and he cruises around London in the same motor in which I used to travel to Brownies. I wonder if there are Wet Ones and a tin of sugar-dusted “travel sweets” in the glove compartment.

Elba’s performance as Luther has been much praised (he won a Golden Globe for it in 2012) but he doesn’t have an awful lot to do in the way of nuance. I prefer Dermot Crowley’s turn as his boss, DSU Martin Schenk; one look at his hair (lank as day-old underwear) and skin (dishcloth grey) and you absolutely believe in him. If you could hand him his police pension there and then, you would, just as an act of pity.

But Luther’s most important character is London. The series is beautifully shot, blues always bleeding into greys and every pano - rama framed or gloriously bisected by some bridge or tower. You watch it and think: this is what album covers used to be like, kids. (Though I also think, sometimes: my God, I’m seeing Blackwall in a whole new light. The location scout deserves a medal.)

So, am I convert? Yes, I think I am. It doesn’t stand up, any of it, plot-wise but it’s still a cut above some cop series. And it stays with you. I keep thinking about a certain stiletto heel, as seen from the perspective of a man who is hiding beneath its owner’s bed . . . Tonight, I will be checking out my boudoir very carefully, just in case.