Tiny Green Beastie

Having trimmed back part of an ivy bush I was cleaning the hedge trimmer when I spotted something tiny and green crawling under the handle. It was difficult to photograph there but eventually it found its way down to the lid of the wheelie bin:





As it was no more than 10mm in length I didn't even notice the hairs until I had the macro lens really close. Those, I thought, should make it easy to identify. Wrong. I gave up after looking at well over a hundred green caterpillar photos and not one was a match.