Posted: 24/06/2014 at 10:47
Claire, your description sounds very like my potatoes. You're supposed to remove the blighted leaves and destroy them. I do find that with Charlotte, the potatoes themselves are unaffected even when the whole top.has died off, and they will stay fresh in the ground until you want them, although they won't grow any bigger.
But some other varieties of potato tuber seem to succumb to the blight, so maybe lift and store them, or eat them first?