Monton Pro Suutu Merino Socks
Soft, warm and cosy, and at their 'reduced' price of £12 these winter socks are quite a bit less money than the competition.
The attention to detail is very impressive. The Pro Suutu socks come as a right and left pair and are shaped so they hug the contours of each foot closely. That seems to really help with warmth because there aren't any gaps or voids for cold air to get at your foot.
A big advantage of merino wool that makes up most of the mix is that it supports the growth of bacteria much less than synthetic fabrics. Where your polypropylene cycling socks will be whiffy after one ride, merino garments can be worn several times before they get smelly.
There's Spandex (aka Lycra aka elastane) for stretchiness, plus nylon and polyester which should help with durability.
But it's the merino wool that has most effect, both insulating when it's cold and helping to wick sweat away from your feet if things warm up, so even if you're still wearing overshoes you don't get too hot - reviewer John Stevenson found on this feet remained comfortable on rides that started in single-figure temperatures and finished in warm sunshine.