Well said, Capetonian, you've got it in one. In the UK, it's nothing to do with security or efficiency and everything to do with chippiness. You're a bunch of rich/idle/good-looking/upper-class/toffs/holidaymakers/lottery-winners etc., and we have to do this crap job all week long in order to make enough money to buy a big TV so the kids can watch X-Factor and we can and will f*** you up for the sake of it.
Anyway, amusing thread, as was the Gatwick N thread on a similar topic. Two nights ago at a quiet T5, with only the Mumbai and Abuja flights left to go out, passed through a deserted fast track security and decided to try the smiley route. Laptop out etc. and then a cheery "Is it a shoes-off day today?" "Yes" came the answer and off came the shoes, but (actually inadvertently) on stayed the belt (under a sweater) and in pockets stayed the keys and small change. Not a bleep, and not a second glance from the bored oaf by the scanner.
Oh, and incidentally, the roll on that was too big at LGW two weeks ago has remarkably shrunk in size so it fits perfectly at LHR.
Hmmm ... all points made, methinks. Total inconsistency. Substantial degree of negligence all around.