Korean Hornbeam Critters!!

A few months back I noticed that a Korean Hornbeam in my garden was being eaten by something. I did the usual search of the leaves but couldn’t find a darn thing. I sprayed with insecticide and left it at that.

Last week I noticed that another Korean Hornbeam, in a different part of the garden was also getting eaten, leaving some leaves like skeletons. This time I spotted the little caterpillars that were doing the damage!

They’ve kind of ruined my chances of decent Autumn colour on this tree now. Has anyone else in the UK had these buggers on their Hornbeams, or even know what they are?