At Snettisham Beach, the dark mudflats riven with water channels stretch into the mists to the west. The myriad worms, crustacea and molluscs that live in the fine sands support over 400,000 wintering waterbirds including around 80,000 red knot; the estuary is also the roost site for around 30,000 wintering pink-footed geese that commute at…