We pulled up to open the farmhouse gate and I noticed a very large moth fly through the headlights and appear to land in front of the car. I got out to check, and found it sitting on the bumper bar - a large moth called a Helena Gum-moth Ododiphthera helena, a male.
With the help of a torch I took its photo and left it where it was while we drove up the lane to the house. It then decided to move camp again, heading for the outside light of the house, so I took his photo again. I'm no expert at moth photography, but the results are good enough to identify it.
We found a caterpillar of the species in exactly the same spot in March this year. It's very similar to an Emperor Gum-moth Ododiphthera eucalypti, but doesn't have a white triangle on its shoulders. The caterpillars are quite different.