In the early 2010’s when amateur drone technology was was becoming affordable, and before legislation was enforced, I built a series of drones that were offered out for public use.
They have been used to get accurate counts of turnout for protests and to peek behind hoardings to see what property developers were actually up to.
Since then, access to drones has become much easier, and laws to their use have been introduced. This has opened up this field of investigation to the general public and my original drones await another purpose.