Last years potatoes

I have potatoes coming up from last year, should I dig them up. I'm not sure whether they're be ok to eat.

A recent thread discussed this and the blight risk 
You'll find it here
http://chat.allotment-garden.org/index.php?topic=105770.msg1186354#msg1186354

Thanks for the advice , we will dig them up ASAP, the volunteer spuds are from the previous owner and they must be deep down  because hubby dug the bed over about three times.
Fortunately there not near where we have planted our first years crop, and I have not sown anything in that part of the bed yet.