Extra checks when travelling to UK
It's been a while since I flew CGN-LGW or STR-LHR a couple times a year, but from what I remember being told at the time, the extra checks on flights to the UK were because the list of prohibited items wrt hand luggage is longer than for other destinations in Europe. (can't remember the items, though. Amount of liquids, maybe?)
The first check that everybody goes through is done to normal standards, and if you fly to the UK, you go through a second check before the gate.