The knife came in a special black cardboard box with the blade wrapped in newspaper and slipped into a protective vinyl scabbard. The steel was clean and bright, stippled along the spine as if it had been beaten with a small hammer, and engraved with Japanese calligraphy. The cutting edge bore a watery swirl, like a trace of fire and smoke, the mark of the grinding wheel.

He slid it back into the vinyl scabbard, laid it in the box and left it on the table.

The old knife was bigger and blunter and no longer cut very well: eggplant, for example, was more of a hack than a cut; so were tomatoes. A friend who’d stayed in the house while they were away once bought it and left it as a thank you with a note about not being able to find any sharp – or had he said decent? – knives in the drawer. After that, he was no longer really a friend, but it wasn’t just the knife.

There was the rustic chopper with a simple wooden handle from a temple festival. A man with a shaved head and a kimono sat beside a pile of them on a mat. He sliced through sheets of newspaper to show how sharp they were. The temple festival knife cost almost nothing, and it stayed sharp for years. It was still sharper than the ex-friend knife.

On the same trip they went to Kappabashi, the kitchen-shop street, and bought a good carbon-steel knife from a knife shop. One afternoon, when they were arguing, he threw it at the back fence, hoping that the point would bury itself in the soft timber, an exclamation point, but the blade had merely broken in two.

His favourite knife came from via Speronari in Milan. They’d had it for nearly 30 years. The blade was worn down from sharpening, and the tip had broken off years ago when he was jointing a rabbit.

The second Kappabashi knife just disappeared. He thought it might have gone into the compost bin under a pile of vegetable scraps and rusted away. Her Japanese sister-in-law had given it to them. Soon, she disappeared, too.

After a few days she said, “Are you going to use the new knife? I’ll be really offended if you don’t. I went all the way to Kappabashi just to buy it.”

The knife gleamed in the downlight and the edge was frighteningly sharp: onion, carrot, eggplant fell away from the blade in clean slices. He cut his thumb with a mere touch, and the blood ran freely. He wrapped it in a plaster and handled the knife like a fish that might slip from his grasp, a dangerous fish that would bite.

The heel of the knife’s blade was unguarded and made a savage right angle with the edge; he cut his thumb on that, too, and wrapped another plaster around it.

He found, by chance, a video on the internet of a Japanese man using a samurai sword, and he saw the knife’s kinship with this other steel. The stippling and the calligraphy on the blade seemed heraldic, as if it were really a small sword that had been captured and tamed – just – for the kitchen.

Here was a thing he learned: use the spine of the blade to push onions from the cutting board into the pan, not the edge.

And another: slice with a downward-forward stroke, rather than cutting straight down.

He looked at the blade in the light, examined the edge, but didn’t dare to touch it. He found a tiny ding, from something hard.

“Don’t worry about it,” she said. “It’s meant to be used.”

When you thought about it, a knife was just a wedge, a very thin wedge that came between a thing and itself, sundering.

But the blade would eventually blunt, or be consumed by sharpening, and he no longer threw knives at fences. ❡