In 1999 climbers found George Mallory's body high on Everest, 75 years after he vanished, and the clothes he died in were still on him. They were wool, silk and cotton. In 2006 somebody put on an exact copy and climbed the mountain in it. For decades the story had been that Mallory and Irvine were doomed by their kit. Tweed jackets and woolly jumpers at 28,000 feet. Brave amateurs, dressed for a grouse moor. The body told a different story. Mallory was wearing 8 thin layers. Silk next to the skin, then fine wool, then more silk, more wool, a flannel shirt, and a windproof cotton outer woven so tightly it turned the snow. Four British universities took fragments from the body and rebuilt the whole outfit, thread for thread. A mountaineer called Graham Hoyland wore it on Everest. He reported that it was warm. It was also lighter than the modern down suit his companions were wearing. The silk layers slid over the wool, so he could move his arms freely, which a man in a padded plastic suit cannot. The wool held its warmth when damp with sweat. He said he would have been comfortable going for the summit in it. The researchers concluded the clothing was fully up to the job. So the gear of 1924 was not the weak point. A sheep and a silkworm had solved the problem of the coldest place on earth, at less weight, before anyone had invented nylon. Then we spent a century replacing it with petroleum and told ourselves the men who came before were underdressed.

The Royal Navy switched its sailors from cotton to polyester two years before the Falklands, and the sea put the two fabrics to the test on the afternoon of 4 May 1982. HMS Sheffield was hit by an Exocet 70 miles off the islands. The warhead did not go off. It did not need to: the rocket fuel did, and the ship filled with fire and black smoke in seconds. Twenty men died. Many more came out of her with burns, and the burns had a feature the surgeons at Ajax Bay and the Uganda had not been trained for. The shirts had melted. The new working rig was polyester, lighter and cheaper and quicker to dry than the old cotton, and in a flash fire it did what polyester does at 250 degrees, which is turn to liquid and bond to whatever it is touching. Men were brought off with their uniform fused into their skin, and the first job in the burns tent was peeling plastic out of flesh. Nylon socks did the same thing to feet. Anti-flash hoods and gloves, the white cotton gear every sailor still wears at action stations, had saved the faces and hands they covered and left a line where the plastic began. The lesson was learned at the Sir Galahad too, at Bluff Cove a month later, where the Welsh Guards were caught below decks and the burns ward at Ajax Bay found the same thing. Afterwards the Navy went back to natural fibres. Cotton action working dress, cotton socks, the wool jumper that had never left. The US Navy took the same lesson from the Falklands and again from the USS Stark in 1987 and banned polyester and Corfam shoes aboard ship. Then, in 2012, it issued a new blue camouflage working uniform, tested it, and had to announce to its own sailors that it would burn robustly and melt into a sticky molten material. The uniform was nylon and cotton. It had been in service for four years. Every navy that has ever had a fire has arrived at the same answer and then forgotten it as soon as the accountants came back. Natural fibre does not melt. A sheep's wool will not catch at a temperature a ship fire reaches, and when it chars it stops. Cotton burns, but it burns off, it does not become part of you. The shirt that went into a man's skin on the Sheffield is the same fabric as the school polo shirt, the fleece, the gym top, the sofa cover and the sheet on the bed. The Navy had to be shown it once. You are wearing it now.

In the first series of Clarkson's Farm, a young woman told Jeremy Clarkson his sheep would never make money, and the wool cheque proved her right before the year was out. Ellen Helliwell was the shepherd he hired when it became clear he could not manage 78 ewes himself. She lambed them through the night, treated their feet, and told him the arithmetic at the start. Then came shearing. A gang arrives, charges by the head, and leaves a pile of fleeces. Clarkson sent the wool off and learned what every sheep farmer in Britain already knew. The fleece was worth less than the cost of taking it off the animal. For 800 years that fleece was the wealth of England. It paid for the cathedrals and the wars. A sheep was kept for five or six years for her wool, and the mutton at the end was a bonus that fed the country. Now the wool is a disposal problem, so the only thing a sheep can earn from is a lamb sold at five months. One income where there used to be three. Clarkson's flock lost money, and he said so on television. The reason the fleece is worthless is in your wardrobe. The jumper is acrylic, the fleece jacket is polyester, the carpet is nylon, and all of them are made from oil. Ellen could do everything a shepherd has had to do since the Bronze Age, and do it at three in the morning. The thing she could not do was compete with a plastics factory. Check the label in your collar before you ask why British lamb costs what it costs.