Strike’s Cornish roots are revealed as he examines the mysterious disappearance of a 29-year-old doctor in the area in 1974 — as is Robin’s anguish over her failed marriage.

The ingenious killer is captured with a gimlet eye, proving the old adage that a good hero is always made better by a great villain. Intensely satisfying, though it is very long.

One of the many strengths of this very enjoyable novel is the way in which it traces the consequences of crime for all those survivors affected by it. “Crime,” as Nicholas Freeling wrote, “is the pathology of the human condition, the moment at which … the delicate balance of metabolism tilts into morbidity.” This is what we are shown here. The solution, scrupulously arrived at, may, if stated boldly, appear far-fetched and improbable. But it has been well prepared. The clues have been planted. Careful reading is rewarded. Yes, it is bizarre. Yes, it may at first seem to strain credulity. But this is the case with murder – it leaves one astonished, even perplexed, especially when the killer’s choice of victims may appear haphazard, the motivation barely comprehensible.

A new novel by JK Rowling’s crime-writing alter ego is always an event. The fifth volume in her bestselling Cormoran Strike series is a heavyweight in every sense, unrolling the latest case of her mercurial private detective over 927 pages. At such length, there could easily be longueurs, moments when the plot is held up by the author’s intense engagement with the characters, yet the story is injected with a powerful sense of urgency. That’s even more impressive when you realise that the case Strike and his partner, Robin Ellacott, are investigating is 40 years old, dating back to the evening in 1974 when a young GP walked out of her practice and disappeared.

Brilliantly brought to life on-screen by Tom Burke and Holliday Grainger in the BBC1 adaptations, Strike and Robin’s personal narratives benefit from the depth and sparkle of the pair’s on-screen portrayal. I am lukewarm about the will-they/won’t they tension, and wonder whether the author feels, as her characters do, that getting together risks ruining a good thing. Both seem to end this story in less self-destructive states than at the beginning, though not without some major bumps along the way. Good news for Robin and Strike, but not necessarily for the reader who has taken the journey with them.

Rowling/Galbraith is well aware that the unresolved sexual tension between her detectives is an element relished by readers, and that’s channelled here as Robin, in the throes of a chaotic divorce, tries to identify what she feels about Strike (Robin is the recipient of some unwanted male attention – not from Strike – and there is a critique of toxic masculinity here).

But while the earlier books have been weighty enough, this one really is an epic exploration of the kind of case Christie and Chandler dispensed in a fraction of the length. Still, there’s no denying the fact that Strike’s creator justifies the inflation with rigour and intelligence, and she makes the most of her English settings, such as the bracing (if past-its-prime) seaside town of Skegness.

Those wishing to immerse themselves again in her seductive world of criminality will have no complaints.

A scrupulous plotter and master of misdirection, Galbraith keeps the pages turning but, while much of Troubled Blood is terrific fun, it is hardly a hair-raising ride. With jeopardy thin on the ground, the languid pace and the elderliness of the mystery (and indeed most of the suspects caught up in it) combine to give the enterprise the unthreateningly cosy air of old-fashioned Sunday night TV drama. When the denouement finally comes, it is not quite satisfying enough to justify the page count.

Strike and Ellacott, however, remain one of crime fiction’s most engaging duos. 

Rowling/Galbraith always writes well about her characters’ personal lives, although there is nothing here that quite matches her superbly well-observed portrait of the breakdown of Robin’s marriage in the last book. Nevertheless, Rowling’s recent revelation that she was sexually assaulted as a young woman adds an extra poignancy to her depiction of how Robin’s similar experiences drive her desire to help life’s victims. The meat of the book is the investigation into a cold case: the disappearance of GP Margot Bamborough in 1974, thought to have been a victim of Dennis Creed, a transvestite serial killer.