As the Shore crab (Carcinus maenas) is the most common crab found in rock pools on British beaches, I assume this dead crab I found on a local beach is one of those.

The reason I can’t be sure is that you need to check the pattern of spikes on a Shore crab’s shell and, as you can see, this one was missing its shell, presumably because a seabird removed it to feast on the meat inside.