Back when I was a teenager we saw an Elephant Hawk Moth caterpillar walking along the garden path. It was the size and shape of a perambulatory chipolata.
As it was clearly close to pupation we kept it safe until it hatched and then released it.
That was in Derbyshire. Privet Hawk Moths were relatively common on the Oxon/Bucks border. No idea whether they still are.