Comment by ErroneousBosh

The fact that nobody has flown a drone with a hand grenade gaffa taped to it right into the middle of some politician's security cordon says to me that either a) terrorists are not smart enough to go for the low-hanging fruit (and the Republican terrorism in NI demonstrates this isn't the case), b) it's actually a lot harder to do than that, or c) the intelligence agencies are really, really good at stopping people from doing that, and even better at keeping quiet about it.

I'm going with option C.