Nikon D5200 Tamron 70-300mm f32 130mm +68mm 1/60 ISO 1000
I had this down as a Yellow Slug – Limacus flavus, but David Nicholls of NatureSpot helped me identify it as Limacus maculatus. Both species are quite variable but the Yellow Slug is more lemon yellow and has a clear pale line along the keel, from the tail to at least half way along the body. This species has been expanding its range across Britain and seemingly replacing Limacus flavus along the way. It may be under-recorded due to confusion with Limacus flavus but it is expanding its range. These changes are one reason why citizen science nature recording sites such as NatureSpot (for Leicestershire and Rutland only) and iRecord (all the UK) are so important.
Eggs, likely from the same specimen: