Inside the robata: charcoal, fire, patience.

The robata grill in our kitchen runs binchotan — Japanese white charcoal made from oak, fired at very high heat for a long time, and broken into dense, ringing pieces that look more like rock than wood. It's the cleanest-burning charcoal there is, almost no smoke, almost no flame, just a steady infrared heat.

It also takes forty-five minutes to light. We start at 11.30am for a 5pm dinner service, and the head chef on the grill won't put a single skewer down before the binchotan has come up to about 700°C and stabilised. Rush this and the grill smokes, the flavour goes off, and a £42 portion of wagyu sirloin tastes like every other £42 portion of wagyu sirloin in London.

The dish that has been on the robata board the longest is the chicken thigh yakitori. Three pieces of dark meat from the thigh, spring onion in between, glazed at the table in a tare we've been topping up with the same starter since 2001. Forty-five seconds a side, two flips, no more. The skin should crackle, the centre should still be just-cooked.

Other regulars on the grill: the wagyu sirloin (sliced very thin, seared sixty seconds total, finished with truffle salt and a little gold leaf), the lamb chops with miso glaze, and the half aubergine that has converted more vegetarians than any other dish on the menu.

The discipline of the grill is what makes the difference. There are good Japanese kitchens in London that gas-fire their robata. There's nothing wrong with that — gas is consistent and easier to staff. But the difference in finish, in colour, in that very specific char that only comes from binchotan, is the difference between food and food worth booking for.

If you eat at the counter, you can see the chef working the grill in front of you. If you sit in the dining room, you'll smell it before the plate arrives. Either way, that's twenty-five years of one cook, one fire, one technique. We don't think it'll ever change.