I got three questions. An elderly lady in the front row asked me about Foyle’s War. A kid at the back wanted to know if there was going to be another Alex Rider and if so, would it have better gadgets? And a strikingly attractive fair-haired woman with ice-blue eyes made a lengthy speech about the importance of school libraries and asked me what I would do to save St Anne’s, by which I think she meant the school rather than the entire town. This is actually something I know quite a lot about and I remarked that under UK law, libraries are statutory in prisons but not in schools. This happens to be true and, with this audience, it went down well.

But after that it was all Hawthorne. Did he believe in the jury system? Did he support capital punishment? Did he like reading detective fiction? Had he ever watched Midsomer Murders? (No.) Was his picture going to be on the front cover of the book? Who would play him in the TV series? On and on it went until Matheson raised a hand and said that we were out of time.

There was one person in the audience who hadn’t been allowed a question, even though he had tried several times to attract Matheson’s attention. It was the man in the third row who had come in with le Mesurier, and before anyone could stop him, he pulled himself laboriously to his feet and called out: ‘I have a question.’

‘Actually—’ Matheson tried to cut him off.

‘Detective Inspector Hawthorne hasn’t told us why he left the Metropolitan Police. If he was so successful at his job and they liked him so much, why did they kick him out?’

I looked at Hawthorne. To the audience, it would seem that nothing had changed. He seemed relaxed. His face gave nothing away. But sitting with him, I got the sense of a coiled spring. Right then, I was quite certain that the two men knew each other.

‘You’re mistaken,’ Hawthorne said. ‘I wasn’t kicked out. I decided to leave.’

‘So there’s no truth in the story that you were dismissed following an assault on an innocent man while he was in your custody?’

‘Not me,’ Hawthorne replied, mildly. He cocked his head. ‘And not innocent, as I recall.’

The audience was looking from one man to another, puzzled and a little concerned.

‘So there was no IOPC investigation? No dismissal for gross misconduct?’

‘Definitely not.’

‘Well, my mistake.’ The words were laced with sarcasm. The man had made his point. He sat down.