‘We cross-reference every vehicle-related fire against the national database of stolen vehicles and persons of interest,’ Naylor continued. ‘Of course it’s entirely possible that Mr Delaney’s car was stolen by joyriders in a completely unrelated incident, and then torched to destroy evidence. Happens every day somewhere in London. It’s possible that’s what happened with the Porsche – except for a couple of things. First: he hadn’t reported his car stolen. And second: because the fire didn’t take hold properly, a lot of the car escaped damage. Whoever tried to torch it was very much the amateur arsonist, didn’t know what they were doing. So even on a fairly cursory initial examination, we were able to recover forensic evidence from inside the vehicle. Including traces of blood on the front passenger seat.’

Naylor let that hang in the air for a minute.

‘Blood,’ I repeated, dumbly.

‘Traces, yes.’

‘Do you know whose it is?’

‘I’ll get to that in a minute. First, a bit of history.’ He took out another sheet from his folder. ‘Last year, Mr Delaney was involved in a minor traffic accident on the M6. No serious injuries – he was lucky – but when his vehicle was being repaired they found his brakes had been tampered with. Police investigators then found microscopic traces of blood on the damaged brake cables. As part of the investigation,’ Naylor continued, ‘they took a DNA sample from Mr Delaney so they could cross-reference it with the trace evidence and ensure he wasn’t the source.’

‘So did they get him?’

‘Who?’

‘They guy who did it.’

Naylor flipped a page in the green folder that had been handed to him a few minutes before.

‘No. A former employee of Mr Delaney’s was charged and went on trial but he was acquitted. Matthew Goring.’

‘That name rings a bell.’ Though I couldn’t remember where from.

‘Anyway, the long and the short of this little piece of history is this: Mr Delaney’s DNA information went into the database. And it turns out that his DNA is a match for the blood we found on the passenger seat of his car yesterday.’

‘I’m sorry to hear that. But why are you telling me this?’

Naylor shrugged.

‘Just wondering if you can shed any light on it, that’s all.’

‘But I’ve told you everything.’

Naylor considered this for a moment.

‘Does it bother you that Ben Delaney’s a self-made millionaire and you’re a teacher?’

‘Not particularly.’

‘Does it bother you that he has a six-bedroom pile in Hampstead and a fleet of flash cars to turn ladies’ heads?’

‘Honestly? No.’

‘And what did it feel like,’ Naylor said, leaning forward, ‘when you found out he’d been fucking your wife?’

He slid the swear word in quietly, almost gently, like a stiletto between my ribs.

I looked from one detective to the other.

‘You seriously expect me to answer that?’