I'm certain that if someone with evil intent wanted to use a helicopter for any purpose they wouldn't be so stupid as to fill a form out and submit it in advance to the authorities for prior approval!
Agreed (no sh1t!). But...
Just as no-one checks who is in a private car or hired taxicab driving between two private addresses
In my limited experience, the police do exactly this. Some years back I was driving to Lossie and was making good time on the A9; a patrol car clocked me, tailed me for about a mile then pulled me over, by which time they had already checked that the car was MOD owned so my explanation of what I was doing in deepest Scotland late at night with several holdalls on the back seat tied in with what they could find out in 30 seconds of checking as they followed me. I totally take your point that no ID is required for persons on a GA flight within the UK, but maybe the point of what the police are doing is to make the baddies aware that GA is being monitored and therefore not a foolproof way of achieving their evil aims. Of course there will be ways of dodging the law, and certain officers of the law may make an a$$ of themselves as they try to monitor us going about our business, but as several people have said, doing nothing at all isn't an option. Was it Anthony Eden who said "A leaky dam is better than no dam at all?"