Actually, I didn’t say any of this, much as I wanted to. I’d just had the worst two days of my life and I was terrified that the next two were going to be worse still. What would happen if Hawthorne failed to find the killer before the DNA evidence came in? How was I going to tell my sons that I was about to be arrested for murder? Of course I wanted to tell her, but I couldn’t bring myself to do it. Jill had enough on her plate running a company, currently raising the finance for an eight-part series based on my Alex Rider books. There was nothing she could do to help me. This was something I had to deal with on my own.

‘I saw Hawthorne,’ I said.

‘Oh – really? I thought you weren’t going to do another book with him.’

‘Well … he’s investigating something that might be worth thinking about.’

She was surprised. ‘What about Moonflower Murders?’

That was a mystery novel – fiction rather than true crime – I had been working on for six months. I’d worked out most of the structure, but so far I hadn’t written a word. Would they let me have a laptop in jail? I doubted it.

‘I might write some of that tonight,’ I said, vaguely.

That reminded her. ‘Where were you last night?’ she asked.

I’d known she’d ask me this and I’d already rehearsed my answer. ‘I went to see Ewan Lloyd. He has a place in Finsbury Park. We had rather too many drinks together and he invited me to sleep over.’

I hate lying to Jill. We’ve been together so long and she’s so much cleverer than me that it makes no sense to keep anything from her, and anyway, she always finds out. But this time I felt I had no choice. My one hope was that someone would say something or some clue would fall out of the sky and Hawthorne would work it all out. That was what I told myself. She would never need to know.

‘Did you see that a theatre critic got killed?’ Jill asked.

‘No!’ I was amazed. ‘Which one?’

‘I’m surprised Ewan didn’t tell you about it. I heard it on the news.’

It was a wretched evening. We watched a TV show together: season 7 of Game of Thrones. I could never work out what was happening at the best of times, but given everything that had happened, I wasn’t even able to enjoy the gratuitous sex and dismemberments. After an hour, I went up to my office and tried to work, but my thoughts were as blank as the computer screen in front of me. I was tired and wanted to go to bed, but knew I wouldn’t sleep, so I abandoned my desk and took the dog – a chocolate Labrador – out for a walk. It might at least be a chance to clear my head.

It was a little after ten thirty and a particularly dark night in Clerkenwell. At least it was still dry, but the streets were deserted and the moon was hiding behind an impenetrable bank of clouds. One of the joys of living in this part of town was its sense of remoteness, the way it retreated into the nineteenth century as soon as the offices emptied and the pubs and restaurants closed. My flat was on Cowcross Street, literally where the cows once crossed on their way to the meat market. Nando’s, Starbucks and Subway had all muscled their way in – our one bookshop had been forced out fifteen years ago – but the area still clung on to its sense of history, with St Paul’s Cathedral watching over in the distance.