Dave, you cannot leave your house for a short trip in London without being picked up on hundreds, if not thousands of "Spy" cameras. They are allegedly there to catch criminals.
It is difficult to buy cans of spray paint, because of all the Graffiti Morons stocking up.
So how come, no Graffiti Moron has ever been caught spraying their rubbish all over the place ?
I had a dream in which someone affixed a spray can of paint (with a string-actuated release) to the end of a long pole and accidentally released paint at the exact moment that the can was in front of the spying device, coating the lens with an opaque film (color undetermined). It was an innocent faux pas.