In reply to Glyno:
Darn tough are very good.
But as Toby A says look at boot fit which could be the cause. If space and circulation constriction is the issue consider trying a thinner footbed, less tight lacing and less sock thickness, or combination of the above. Also check your gaiter calf strap or even sock elastic isn’t cutting off blood supply.
Very unusual to get cold feet winter walking when you are moving all the time, unless your feet are soaked or using very light boots, or have an underlying medical condition?
Post edited at 22:22