Not sure I agree entirely. A guy with a shotgun in a helicopter could of done it, both of which were available at Gatwick. The shot looses velocity quite rapidly so wouldn't do much damage on the ground. I guess you'd have to hope the drone didn't land on anything much.

Londoners mostly got though the Blitz ok with a million houses destroyed or damaged by bombs. We can handle the risk of a crappy drone crashing in someones garden. https://en.wikipedia.org/wiki/The_Blitz#No_collapse_of_moral...