Cock-tail beetle

We found this rove beetle, Ocypus sp. (possibly nitens) running across the garden patio. It lifted its tail briefly a couple of times, honouring one of its common names 'cock-tail beetle', but afterwards it decided to groom itself at the bottom of the white bowl. These are usually nocturnal and predatory, often found under stones and logs during the day. They are quite fast and usually hide before photos can be taken in their natural habitat.

UPDATE Fauna, from Wild about Britain, suggested that this is Tasgius (which used to be Ocypus). I am thinking T. ater, as it has a very shiny head. The enlarged tarsi makes it likely to be a male.