Just remembered: Donkey's years ago, calibrating the ILS at RAF Gatow, Berlin, in an Argosy, we noticed a family picnicking right on the C/L just at the perimeter fence.
On the next approach we had the loo washbasin filled and, as we passed overhead, the nav pulled the plug. Next approach, they were gone.
How were they to know it was just clean potable water?
