I think it's a white-clawed crayfish. They can get to about 12 inches.
They're protected, because the American signal crayfish has invaded the rivers, bringing with it a crayfish plague that it is immune to, but the native crayfish is not.
I don't think this is an American crayfish, because its claws aren't red enough and it doesn't look quite as angry. But I could be wrong.
I think he's mislaid parts of himself.
Crayfish are clumsy like that.