In those days, says Wheen, boarding school was “like being in prison, shut off from the outside world, so the only people you see are the other pupils there and the teachers. And we couldn’t communicate with the outside world very easily. There was no telephone there, that we could use. The only way of communicating was through letters, and they were all censored.”

Napier, who is half-brother of John Whittingdale, the Culture Secretary, left the school in the early 1970s and went on to hold jobs working with children in Egypt and Sweden. He was convicted of child abuse-related offences in 1972 and 1995, but continued being employed in positions of trust.

In 2012, Wheen noticed that Napier was speaking at the Sherborne Literary Festival. Appalled at a convicted child abuser being given such a respectable platform, Wheen told his colleagues at Private Eye how he was assaulted by Napier as a child, and the magazine published his revelations.

“That was what kicked it off. The police got in touch with me and said, ‘Could I put them in touch with anyone else who’d been abused by Napier?’” says Wheen. “The police then spent ages tracking down pupils from the late Sixties, and they did a hell of a job. They managed to get school records, so everyone there, every boy who’d been at the school between 1968 and 1971, and as many as they could find, and in the end the numbers kept going up and up and up, by the end of them it was over 30, I think it was 34 different boys he was charged with, it kept going up. Even days before court they were adding more charges, and that was a school that had 100 pupils, basically something like a quarter of the school was being targeted by him. I certainly had no idea, that if I’d looked around in my classroom, even being there I wouldn’t have realised it.

“That’s it — so much of it is hidden, so much is not spoken about, that’s why it’s so startling when things do start being revealed, you think surely not. But more often than not, it does turn out to be the case.”

Last year Napier was convicted of sexually abusing 23 boys between 1967 and 1983, and sentenced to 13 years in prison. The judge remarked that a number of his victims had been profoundly affected by the abuse, with one committing suicide, and others seeking help for mental ill-health.

Wheen, who waived his anonymity in order to speak out against impunity for sexual predators, was in court for the verdict. He says that he was relieved to hear the judge make it clear that men like Napier do not escape punishment for abusing children, even if a case is brought against them decades after the fact.

Napier’s conviction was not, however, the end of the matter for Wheen. “Soon after [the case],” he says, “I had a letter from O’Carroll, complaining I was being very unfair to his friend Napier, and if only I could understand, and that Napier was a very brilliant, witty chap, and it was very cruel of me to write about him like this.

“I also received a letter from some woman in the social services department, who told me that [child sexual abuse] was a complicated issue and I shouldn’t be tabloidy about it. There are still plenty of people today it would seem who think child abuse is not such a terrible thing.”