According to people up at the allotment site there is a big problem with wireworm attacking potato tubers. The holes these pests make are then exploited by slugs, which enlarge the hole and devour the tuber from the inside. Many people have given up planting potatoes at all. You can minimise the damage by only planting First Earlies, which can be harvested before they are destroyed. I am going to do this, but apparently another allotment holder has discovered that burying a couple of organic slug pellets in the planting hole with each seed potato prevents any damage happening at all. I am going to try it out.