appears to be very short and fat, light brown colour, found on tree stump
No interactions present.
Another one of the larger Arion spp. A tip to help narrow it down some, is to prod it slightly when it is in this position. You will probably see this one dance from side to side, which Arion ater and A. rufus does quite well.
Lat/Lng: 51.8, -2.5
OS grid ref: SO6713