I once had a farmer write all over my (white) Four in black marker - across the windows and bodywork. Apparently I'd parked on part of his road that I shouldnt have, despite the signs not saying this and the fact that I was rather desperately looking for 6 lost teenagers who could have been anywhere in a 20sq mile area, in the Lakes.
He stood by and was very pleased with himself, I simply didnt say a thing (despite wanting to nut him) - and popped out my map-cleaning meths and a cloth and wiped it all off with a quick swipe. Must have *BLEEP*ed him off.