Five series of Clarkson's Farm, and the same thing happened every year without anyone pointing it out. The wheat drowned in the wettest autumn on record. The sheep stood in the rain and lambed. The oilseed rape was eaten by flea beetle before it came up. The cows ate the grass that grew where the rape had failed. The potatoes rotted in a shed he could not sell them from. The pigs ate the potatoes. The wasabi, the chillies, the mushrooms in the bunker and the nettle soup made a few hundred pounds between them. The venison off the wood paid for the stalker and then some. The barley came in late, light and under the price it cost to grow, and the brewery took it at a discount. The beef off the same acres went out of the farm shop at a price people queued down the lane for. The arable half needed a two hundred thousand pound tractor, a man to drive it, a contractor to combine it, diesel, sprays, seed and a prayer to the sky. The grass half needed a fence and an animal. The one thing on that farm that failed every single year was the part a government leaflet tells you Britain should be growing more of. The one thing that never once failed was the part you are told the planet cannot afford. Five years of evidence, a thousand acres, the best advice in the county, and a camera crew to record it. The verdict was the same as every hill farmer's since the Domesday Book. On land like that, the animal is the only thing that works.

People ask me why I'm so obsessed with ruminants. I've given it some thought, and my conclusion is that I'm not obsessed enough. A cow walks onto a wet hillside that grows nothing a human can eat, puts her head down, and comes back with steak, butter, cream and a pair of boots. She does it with a 150 litre fermentation tank she carries inside her, stocked with more bacteria than there have ever been people, which she feeds, waters and keeps at blood heat herself. Grass goes in. The bacteria take apart the one thing no animal can digest, and she lives on what they make. Then she digests the bacteria as well. Nothing is wasted. Even the fat comes out the far side rebuilt into something stable enough to fry in. Fuel: rain and sunlight. Emissions: next year's grass. She repairs herself, builds her own replacement every spring, and improves the ground she is standing on while she works. The finest engineers alive have spent billions trying to copy one chamber of her stomach in a steel shed, and so far they have made a paste. We have leaned on that machine for everything. The word capital comes from cattle, because a herd was the first bank. Domesday Book is written on sheep, and so was every deed in England for 500 years. Ruminants clothed our armies, lit our houses and carried our laws. Civilisation is a thing that happened to people who kept them. And they are such good company about it. A sheep remembers fifty faces for two years, which is forty-six more than I manage. A cow has a best friend, and her heart rate drops when that friend is beside her. A goat that cannot solve a problem will turn and look to you for help, as a dog does, and then ignore your advice. Let a herd out onto spring grass after a winter indoors and half a tonne of animal will skip. They ask for grass, rain, and to be left to get on with it. After ten thousand years of feeding, dressing and housing us, they will still walk over to the gate to see who you are. So no, I will not be calming down.