This is a Devil's Coach Horse beetle I saw on Great Lines, Chatham, this morning. Not a very good photo but I had to use my phone camera since I didn't have a proper camera with me.
It is clearly pretending to be a scorpion, but it has no stinger. Quite what advantage this would give it is unclear since for most of human history people (and any other potential enemies or predators) would have had little knowledge of scorpions in Britain.
Despite the lack of stinger, according to Wikipedia it can hurt you since it has a fairly painful bite. I didn't realise that any British beetle could damage you, but there you go.
Jonathan Brind