I looked out of the kitchen window and saw that my husband S had put his cycle helmet on the roof of my car. I made a big shout of 'Nooooo!' and went out to put it on a nearby hedge.
Is this the difference between people who have a sibling and an only child? I regard taking someone else's territory as an act of war, but S presumably just thinks the roof of someone else's car is a convenient close site for his helmet.
How easily people get in a lather!