CRIME and punishment form a huge proportion of TV: documentary, fiction, even comedy. The standard climax is the apprehension of the perpetrator, or the guilty verdict, but, in ITV’s brilliant drama Des (14, 15, and 16 September), based on the horrific Dennis Nilsen case in the 1980s, the jury had to resolve a far more slippery moral conundrum: was the accused sane or insane?

The defence accepted that the mild-mannered civil servant had, indeed, killed at least 12 young men; but, if he was mad, then the verdict could be only manslaughter — resulting in hospitalisation, with the eventual prospect of release — rather than murder, carrying a lifetime prison sentence. The police and prosecution had to prove premeditation: that he meant in advance to kill.

Many aspects of Nilsen’s appalling behaviour appeared to me to be, in a non-technical sense, stark staring mad. Having strangled his victims, he then kept their bodies around him until the decay became intolerable, then dismembered them and hid the parts in his flat. He spoke volubly about what he had done to the police, and to the author Brian Masters, who was preparing a book about the affair. He wrote reams of material setting out the story.

While desperate for the spotlight and publicity, he seemed weirdly disconnected, as though curiously observing it all from a distance. Yet all who worked on the case were convinced that he was responsible for his actions, knew exactly what he was doing, and was, legally, sane. Eventually, the majority of the jury agreed.

This was magnificent, unsensationalising TV drama of rare psychological acuity, with three extraordinary performances: Jason Watkins as Masters, Daniel Mays as the investigating detective, and, towering above all, David Tennant as Nilsen.

The Australian filmmaker Warwick Thornton sentences himself to solitary confinement in The Beach: Isolation in paradise (BBC4, six parts from 19 September). It is an attractive version of an eremitic calling: his tin shack is idyllically situated, surrounded by tropical ocean. Another departure from the Christian contemplative tradition is his superlative cookery, alleviating his solitude with an array of sauces, herbs, spices, and antique cooking vessels, with which he whips up Michelin-starred delicacies.

He is, though, entirely alone (apart, that is, from three hens and a film crew) and is here to confront, like St Anthony, his inner demons. Despite my scoffing, the long slow takes, sheer beauty, and personal struggle offer genuine consolation to viewers condemned to isolation.

To escape your personal demons, you might — if your sense of humour was, like mine, basically immature — turn to the new series of Ghosts (BBC1, Monday of last week). Alison and Mike have inherited a decayed country house; only she can see the gallery of spooks who infest it, causing constant mayhem. Portraying every stock British comic character, the splendid cast ham it up with infectious relish.