Running

I want to run to work more but I work outside London so have a 1Okm run to the station followed by a 4O minute train journey during which I get freezing cold. Does anyone have any advice on what layer I can take that's light but will keep me warm on the train? I have lots of lightweight breathable things meant for use while you're actually doing the running/cycling/whatever but I'm not sure if that kind of thing is going to be any use.

pretty much anything that you didnt use to run in. take another top (yes merino would be ace) in a backpack or round your waist and when you get to the station go to the loos and change your top for your dry non sweaty one and you will stay warmer for longer than if you just stay in your damp clothes. get the wet one off as soon as poss. makes all the diference to how warm you stay.