Review: David Tennant's chilling performance as serial killer Dennis Nilsen makes ITV's Des a terrific watch

Watching Des (ITV, Mon-Weds, 9pm) the phrase sprang to mind. A drama following the investigation into serial killer Dennis Nilsen – sparked by the discovery of human remains in a drain – this was compelling TV.

At the centre of it was a brilliant performance by David Tennant as Nilsen, the mundane civil servant who killed at least 12 young men between 1978 and 1983.

The officer leading the case, DCI Peter Jay (Daniel Mays), calls Nilsen “unremarkable”, and I suppose that’s true. And it’s that ordinariness that’s so chilling.

Tennant downplays everything, he’s no Hannibal the Cannibal, even though the details of what he did to the bodies of his victims after killing them are worse than anything you might read in a Thomas Harris thriller.

He’s weirdly personable, as if everything he does is normal, it’s the rest of the world that is twisted.

He tells Brian Masters, the biographer who would write Killing for Company, which Des is based on: “If you’re more disgusted about what I did to a corpse than what I did to a living man, then your moral system is upside down and wants overhauling.”

Questions can be asked about whether or not these dramatic reconstructions are a good thing, but Des was so well-written and performed – restrained, unsensational, respectful of the victims – that those questions seemed irrelevant,

As Masters says of his biography: “This is not a celebration this is a warning.”

A warning that evil can be found.

Ambulance (BBC1, Weds, 9pm) is back , this time with the paramedics of London. It’s as dramatic as any soap, and although it deals in life and death, it’s uplifting in that it shows you the best of people.

Line of Duty seems to have sparked a craze for centring dramas around tension-filled police interviews, and now that’s all Criminal (Netflix) is. They’re taut, short dramas though, full of twists and turns.