The large caterpillar

Dad noticed this large green caterpillar on our driveway this afternoon; it's the largest caterpillar he has ever observed in the United Kingdom:

After some research, Dad thinks this is a caterpillar for an Eyed Hawk-Moth, as they were the only British moth species he could find with caterpillars this big. It's been a long time since we last saw a caterpillar this size!