I'm in London for a few months and I come from a very warm country so I don't own a winter jacket. I'll be going back to my own country so I don't want to spend too much on winter clothes which would be a waste. I just want to buy one winter jacket that I can wear over all my clothes. I'm looking for something versatile that will go well over suits and formal/semi-formal and even sportswear. If you had to choose just one winter jacket/coat, what kind would you buy?