Layering is the key to staying warm enough but not too hot on a bike, especially in the chillier months. In that respect, base layers – which seem to have become more popular since we stopped calling them vests – have a definite role to play.
You don’t necessarily have to use a dedicated base layer, just something that won’t get soggy with sweat and isn’t itchy; cotton’s no good but an extra shortsleeved cycle shirt served me for many winters. Proper base layers from the likes of Helly Hansen are made from cosier, less scent-grabbing kinds of polyester.
Rapha’s is unusual: it’s very thin wool. Wool is breathable and insulates even if it gets damp (this didn’t). This top is comfortable next to the skin, not scratchy, and like the better polyester base layers doesn’t get stinky. It’s nicely made, it’s machine washable, and it does its job very well.
But… it’s over £40! For a vest! (£45 for short-sleeved version, £50 for long sleeves.) Merino it may be, but I’d want it woven from the Golden Fleece for this kind of cash. You could get two Helly Hansen Lifa sleeveless base layers for £40.