The Great British Weather

If your legs are not covered you will loose more heat through them.

Pretty much, your blood travel from your heart to your feet, if not covered, the blood will get cool down by the time it reach your feet (echoing tommy).

And I do experience those a lots as I often ride home in the middle of the night, leather glove plus thick soft-shell jacket kept my hand toasty, even if the first few miles was freezing (on the hand that is).

I also have some thick trouser which helped keep my feet warm (combine with wooly sock and boots).