I needed Spoder’s input, though. He had access to internal police material that I could not get hold of otherwise, and his outlook on crimes and the mentality of criminals was usually different from mine. He challenged and refreshed me when he passed material on, even when we had doubled up our searches. Even when his sometimes manic attitude alienated me. As often it did.

Apart from my certainty about his role in the death of Lew, I knew nothing about the events surrounding Dever Antterland.

‘I’m still sorting through what I have,’ Spoder said. ‘I wanted to tell you it’s all here.’

‘Could you bring it over later?’

‘Tomorrow would be better.’

‘I’m thinking about what happened to Lew, his brother,’ I said.

‘Is there a story or a novel in that?’

‘I don’t know at the moment. It probably depends what you have on Dever.’

‘I’ll come to the house tomorrow morning.’

In the middle of the day Jo contacted me from her hotel room in Chor. A business meeting was going on which did not involve her. We spoke online for half an hour. After she had told me about the work she was being offered, she asked what I had found out about the Antterland brothers. I told her how grateful I was for the research she had done. I said I thought that as a result I had solved one case, but Spoder and I were still working on the other. I told her my theory of the murderous twin.

Relating the events aloud made me think again about what I had deduced, what I was saying. I had not consciously thought about this before, and suddenly I opened up to Jo about it. Was there still an allowable, plausible way of plotting a crime novel that involved identical twins?

I voiced this aloud to Jo, putting into words the concern that had been lurking unsaid. Impersonation as an attempt to conceal a murder was an old story device, over-used by thriller writers for decades.

I told Jo I was inspired and excited by the idea of the Antterland case, because it was a real one, not a story someone had made up. I had worked out the modus operandi of a murder, one thought by officialdom to have been a suicide. Then every few minutes I would resile mentally from it, rejecting it because it was so familiar, almost obvious.

I anticipated the embarrassment of putting the Antterland killing into a story or novel, modified and fictionalized in some way, only to have the publishers tell me that I could not get away with such a clichéd idea: not now, not these days, not another one of those identical twin plots. Worse, perhaps, further on down the line having the reviewers and readers say much the same thing.