Based on the 1999 Columbine High School massacre in 1999, the location is a private school in rural Somerset. Perhaps because the author is a former scriptwriter, this novel has a visual, filmic quality, being presented in mostly short scenes, continually switching into flashbacks to fill in the details of various characters. This became overdone at points where the book degenerates into notes – such as a list of newspaper headlines likely to stir up prejudice against Muslims in Britain, or of Trump’s inflammatory tweets.

The novel opens dramatically following the shooting of the headmaster. We are given his increasingly confused thoughts, interspersed with those of the pupils who frantically try to save him, and other staff members taking refuge in various parts of the site, too scared to move. However, I was disappointed that the psychology of the two perpetrators of the crime is never developed and explored sufficently.

In focusing in a period of just three hours in the school morning, the author builds up the tension, as the killer’s footsteps can be heard pacing up and down the corridor, pausing outside the door which cannot keep him (or her) out for very long.

The geography of the site is described in painstaking but hard to visualise detail. It is clearly complicated, with buildings like the junior school or the pottery room set apart – as proves necessary for the plot, but I could have done with the map which the authors of many such novels tend to provide.

The idea of confining the story to a timespan of three hours is interesting, and it is quite tightly plotted, but I found the style too sentimental at times, even “soft-centred”, and so incongruous for such a grim situation, although I did not think it was deliberately intended to create a jarring contrast.

One’s view of a book is always partly a matter of taste, and this one is very popular. However, I was put off by the bleak theme, some overly contrived scenes, not least some admittedly ingenious aspects of the climax, and too shallow treatment of what motivated the villains of the piece.