Wool Fleece.

Fleece is the original egalitarian insulator. It doesn’t give a flying Thermos flask whether you’re a hot-shot rock-climbing adrenaline junkie, or just an average bloke who likes the odd country walk with a pint and some peanuts at the end. Apparently invented in Massachusetts, the eureka moment happened sometime in the 1970s when a couple of textile boffins started playing around with the construction of terry towelling. They subbed cotton for micro-fine polyester and a prototype was born. The version we've been using season after season is made from a wool-based mix. It looks great, washes like a dream and never needs ironing. What's not to like?