Shore Crab - Carcinus maenas
Well I think it is a shore crab, I am not really an expert on crustaceans (except mussels in a white wine, cream and garlic sauce - lovely!), washed ashore during the recent storms. He was busy trying to bury himself in the sand before the gulls and oyster catchers saw him.
Actual size about 10cm across the shell
Made Explore # 415