His T-shirt was covered with blood, and his hand. His mind was racing, chasing through all sorts of permutations of how he might be caught.

‘I just took the knife and ran,’ he tells her. ‘And it’s funny the things that occur to you, even in a situation as shocking and stressful as that. Like how I took care not to step in the blood, how I thought to cover my fingers with a clean corner of my T-shirt when I opened the front door, and the same when I pulled it shut behind me. That I would have the presence of mind not to leave fingerprints … I still thought they’d come for me, though. It was a miracle there was no one on the street. It was so late at that point – past three a.m. A miracle that no one was looking out of their window or driving past in their car.’

It was only when he reached his own house that he realized he had no clue of what to do with the knife. That was when the idea came to him.

Their garden was a mess after the builders. Scrubby grass grew in tufts among the debris left behind after the renovation. They’d had vague plans to clear it up, perhaps put in a patio once they had the money. But neither of them had much interest in gardening. Their focus was all on the house.

‘I picked a spot near the back. It was difficult to see anything in the darkness, but I just pulled at this weed that was as big as a shrub. It came out, leaving a hole that was large enough until I could sort out something later. I pulled off my T-shirt, which was spattered with blood, and wrapped the knife in it.’

He’d covered it over, replacing the weed, then let himself quietly into the house, stripping off the rest of his clothes in the kitchen and putting them into the washing-machine. Then he’d stood at the sink scrubbing his hands, his arms, his face, his torso – scrubbed his skin raw.

‘I stayed on the sofa that night. I was afraid of waking you. Afraid that you’d ask me something and then somehow know what was wrong, what I’d done.’

He lay awake all that night, thinking over various options, all the while alert to noises outside. He kept expecting to hear the whine of sirens, the screeching of brakes outside. But the police never came, and by the time the sun had risen, he had a plan.

‘As soon as it was light, I got up and showered. Then I went outside and began working on the garden, digging it over, like it was a regular Sunday-morning thing to do. Which it was. People are always doing their gardens on Sundays.’