[greenshackle2]

London, sure. If you live somewhere with -25C winters, you either need layers or a set of different jackets, because a heavy down coat rated for -30C will be hot and sweaty if you so much as fast-walk at -5C. I find it more economical to own just a light synthetic jacket and wear extra layers than having an expensive down jacket just for the few weeks at -20C and below.

Layers are also a must if you do outdoor winter activities. You want to remove layers when you're active so you don't get all sweaty, and put them back on when you rest. Because sweat + cold wind is a really nasty combo.

Having said that, as far as I can tell most people in the city here don't do much winter sports and just own like 3 different coats for different weather.