There’s no shame in kitting yourself out with a winter-busting thermal under-layer. Heck, if it’s good enough for grandad, it’s good enough for you – and it’ll save on the heating bill. Unlike thermals of old, today's toasty undies fit like a dream, and no one need know you’re wearing 'em. Just take a look at the video below to learn how to keep warm covertly this January.