A woolly cycling jersey saved my life on the first Alpine Brevet I did (Swiss Sportive with the usual 3500m of ascent in 160km over three big passes in central Switzerland). Somehow, probably because the highest pass was only about 2400m, I expected it to be cool but OK and didn't take a jacket. What with the thunderstorm, snow, 40km downhills etc. I would have got seriously hypothermic had it not been for the insulating properties of the wool even when wet (assisted on the descents by the reknown folded newspaper). I tell you, I felt like a hero from the thirties TdF thrashing up the Oberalp in hail and lightening. By the end, descending into Biasca in the afternoon, the temperature was about 35C, which made quite a difference to earlier in the day, but the woolly was still comfortable enough (and dry).