There is no other material on earth that can do what a fleece does, and it grows on an animal that eats grass. It keeps a sheep alive on a Welsh hill in February, in sleet, with no shelter. It keeps a Bedouin cool in the Sahara in August. It keeps a person warm when it is soaked through, which is why mountaineers wore it to the top of Everest. It will not burn. Put a match to it and it chars and goes out, which is why it lines aircraft seats and theatre curtains. It absorbs a third of its weight in sweat and gives off heat while it does it. It blocks the sun. A wool shirt has the ultraviolet rating of a decent sunscreen. It does not smell. The surface stays too dry for the bacteria that make a shirt stink. It stretches a third of its length and springs back, so a sock holds its shape for years. It stops sound. Recording studios and classrooms line the walls with it. It stops cold in a loft as well as fibreglass does, without the itch. It soaks up oil, which is why the mats laid on spills are made of it. It dyes deeper than anything, which is why a Persian rug is still red after 300 years. It felts into a tent that a Mongolian family lives in through a minus 40 winter. And when it finally wears out, it rots into fertiliser, and the next sheep eats the grass it grew. Every one of those jobs now has a synthetic doing it worse. The sheep had all of them covered before the chemist was born, and it does it again every spring for nothing.