Did you leave your tank full by any chance, Paul? If so the petrol may well have expanded in the heat and overflowed out of the filler.
Nice to see you're still enjoying your car at every opportunity, I really miss mine so need to get my Speedster on the road asap.
You have my deepest sympathy regarding wife borrowing pressure washer for you to use. Mine has plans for me to do some 'gardening' (whatever that is) today.