Anonymous Caterpillar

The small grey stick on the floor under the dining table was not, as I had thought, the stalk from a pear but a caterpillar - and a rather sick one if indeed it had any remaining life at all.
As Mr Flum has been cutting the hedge I expected it might be a privet hawk moth caterpillar so while awaiting a positive ID, I tucked it into a cosy box and gave it some leaves to munch on in the meantime.
Despite extensive enquiries on internet I cannot find an ID and, on further examination, neither is it alive.
Someone on Blip is sure to know - I hope it was not a rare specimen.