It was AA Gill who sent me to eat at St John, about 15 years ago. I went there alone, so compelling a case did he make, and I ate as much as I could off the menu. After my meal I remember tottering unsteadily into the kitchen, getting on to my knees and bowing down in front of Fergus. It really was the restaurant of my dreams. I loved absolutely everything about it: the attitude, the look, the food, the wine.

We became friends shortly afterwards and I'd go to St John every time I came to London. I advocated for a reprint of Nose to Tail Eating with my American publisher. Back then, a book concentrating on offal and heads and snouts was not an easy sell. Now, of course, he's a huge hero in the States. Chefs all over America have pig tattoos and "I love bacon" across their chests and "offal" printed on their hand. He completely expanded the larder and gave chefs permission to cook the parts they'd always wanted to cook.

His roasted bone marrow is simple, austere yet luxurious. It's basically a three- or four-ingredient dish, totally without pretence. He identified a great underused ingredient and a perfect way to serve it. I joke about it with him all the time. Every chef gets stuck with a signature dish that they cannot ever take off the menu, and he's going to have to serve it and talk about it for the rest of his life, and that's a mixed blessing. Fergus's repertoire is far deeper and ever changing, but that dish is so popular, so influential and so closely associated with him

He's a loyal guy, with zero vanity, zero pretence, and a "who me?" attitude towards his fame and influence, which of course is totally charming. When he comes to do a talk in the States, the line will be around the block and the entire auditorium will be dead silent. Fergus is not easy to understand for working-class kids from middle America – he's got an accent they're unfamiliar with and he speaks faintly – but I've never seen more attentive audiences in my life.

He's an old-school guy in a lot of ways and extremely regular in his habits. You know where to find Fergus at almost any time of the day. He's at Bar Italia for his breakfast and his fernet, and he's swinging by the French House whenever it opens, then it's Sweetings for lunch. I don't know how he does it, because you walk into the Groucho Club at closing time and there he is still going strong. If you go back to his house afterwards, you find Damien Hirst unconscious with his head in the refrigerator, and people passed out in potted plants, but Fergus is somehow still going. He apparently never sleeps.

He is a walking Buddha to chefs all over the world, a total rock star. He opened the doors for people to start questioning the conventional wisdom of the restaurant business, built up over hundreds of years. He absolutely changed the world, and now everyone wants to cook like Fergus.