Slug damage for sure. Probably the Black Keeled Slug, very common and can cause a lot of damage to potatoes in a wet year. The main characteristics are a very small entrance hole with a excavation of a cavity in the tuber, which can be slight or extensive. Maris Piper is a variety which is particularily enjoyed by slugs. Not a lot can be done to prevent damage to potatoes other than slug pellets under the plant canopyduring the growing season, but must be done with care to prevent ingestion by non target organisms.
