I know what this means now, but I’m a bit sad about that. I liked it much better when it looked like a sign for wizards, or for almost-wizards with magical flying motorbikes. “Caution, Muggles below!”
Part of living over here is learning all sorts of things you thought you knew how to do already: which way to look when crossing the road, how to lock a door, and what the various signs mean. I do actually know what this sign indicates, but to me, it always looks like a parking sign for a couple and their Dalek. It’s just a shame I never seen such a family getting into these spots.