Gypsies (and stray cats) always leave a mark for those that follow them to indicate a household that is welcoming. Those marks are often if not always invisible to the uninitiated, but lead the above mentioned culprits to your door, looking for hospitality and maybe a little scritch behind the ears.
I think one such sign is at the front of my property. Either that or Fenwick (look here for the beginning of the saga) has a girlfriend who I have never met, and has taken on responsibility for his progeny. It could even be his girlfriend I suppose. Beardy girls might be all the range in garden gnome world, but I'm too polite to ask.
Or perhaps, just perhaps, MY NEIGHBOURS ARE COURTING DEADLY NINJA STYLE REPRISAL TACTICS.
But it's probably the sign thing, like I said.