Bri-nylon was a supplement to Weightwatchers back in the 1980s as you could easily sweat out a few pounds with a long day in the mountains.
These were the days before Gore-tex and companies like Henri-Lloyd were using all kinds of materials for keeping out water. In Henri-Lloyd’s case they were experts in sailing clothing and sailors don’t sweat much (except in a big storm) whereas mountaineers and hillwalkers do.
Note that cagoules of all varieties were longer back then…they came to just above the knee and they wore gaiters to just below the knee so only your knees got wet.
These cagoules were pretty waterproof though, and if you could deal with the perspiration you stayed dry-ish.
This one would have been made by Henri-Lloyd and retailed in Joe Brown’s shops – hence the logo.
Our pal, Ken MacTaggart donated it having sweated it out.