When I checked on him today he had finally vacated this leaf - his sole home since his last skin change - and, I hope, gone off to pupate somewhere. I will search for his pupa at the end of the week, when it should be easier to spot than a caterpillar on the back of a leaf.
Before leaving he consumed a considerable amount of his seat leaf, including much of the silk he had been using to stick his rear end to the leaf:
Assuming he is now laying himself up for pupation, that was his last supper - ever. Once the process begins he will take no more solid food for the rest of his life. What is in his tummy now has to sustain two to three weeks of pupation followed by two to three weeks of dog-fights and sex, supplemented only by a few vitamins and minerals from fox and beech marten excrement.