Des review: David Tennant proves his versatility as he plays one of Britain’s most notorious serial killers

In January 1983, police visited the north-London home of a mild-mannered 37-year-old Scottish civil servant, Dennis Nilsen, who worked at a Job Centre and kept himself to himself. Human remains had been found in his drains. It was the start of a series of extraordinary revelations which would expose Nilsen as one of Britain's most notorious serial killers, a quiet monster who had killed at least 12 young men and boys since December 1978. Two years after Nilsen died in prison he is being given the ITV treatment in Des, a three-part series running on consecutive nights this week.

David Tennant plays Nilsen, the latest effort in Tennant's attempt to prove no actor is more versatile. Even by his standards, 2020 has been a wide-ranging year. In January, he played the goody two-shoes doctor suspected of murder in Deadwater Fell on Channel 4. Then he returned to comedy with Staged, a lockdown concept in which he and Michael Sheen played locked-down actors. That was less of a stretch of his skills than this, in which he has to grapple with one of the worst criminals in recent British history. Nilsen didn't resist arrest, and cooperated with the investigation. With no "who", the question hanging over Des is why. What made this unassuming man do these terrible things?

Daniel Mays, back on more solid ground after the iffy White Lines, plays DCI Peter Jay, the detective tasked with bringing the facts to light. The first problem is that Nilsen can't remember the names of his victims, who were often mentally ill or addicted to drugs. Nilsen would pick them up with an offer of food or shelter, and take them back to his flat where they would drink and chat before he strangled or drowned them. Tennant, his face partially hidden beneath a thick fringe and large wire-framed glasses, uses Nilsen’s accent – mildly Doric, to my untrained southern ear – to great effect, letting words fall off to punctuate a particularly heinous crime. His Nilsen isn't likeable, exactly, but he seems reasonable.

The case attracts the attention of Brian Masters (Jason Watkins), a biographer who sees the opportunity for a book. Masters is gay himself, and Watkins is instantly convincing as the Capote-ish figure trying to establish a rapport with a killer. Between the two inquisitions, Nilsen emerges as a vain, arrogant psychopath, haunted by his own sexuality and all too aware of his value as a story.

Des is made to last. It has a confident script directed with a good sense of time and place. Smells are everywhere: the bodies rotting for more than a year under Nilsen’s floorboards, the tyres he burnt to mask the smell of burning flesh, the still air in the interrogation rooms, thick with cigarette smoke. How could all this happen, right under the policemen's noses? Nilsen’s crimes are grounded in the economic misery of the early years of Thatcher's government, which forced desperate young men into shadowy half-lives, undocumented and vulnerable to predators. Although Tennant’s turn naturally draws the eye, there are fine performances from all the leads.

“It totally amazes me, people’s attraction to the macabre,” Nilsen tells Masters. “Because all of us have skeletons rattling around in our cupboards, you know, secrets they would never dare to tell to anyone, so what comes is this flood of self-righteous public condemnation whilst simultaneously everyone’s talking about it over and over. They’re consuming it, and indulging in it, but at arm’s length."

“I’m here to comprehend,” Masters replies. “Because the law cannot comprehend, beyond guilty or innocent.” Like all good true crime, Des constantly asks us why we are watching. We like to tell ourselves we care about the victims, or understanding the killer, but these may simply be excuses for our fascination with the gruesome.