Originally Posted by
corporate-wage-slave
then the chances are that you are up for the "SSSS" special screening for the day. You may want to minimise your hand luggage (not often I say that!) to expedite things, but all it really amounts to is a more thorough screen of your possessions and answering questions about where you are going and why.
If you're running late for the flight (e.g. from a connecting flight) they may not bother to do it. It's usually after the final gate and before the aircraft doors, on the long metal trestle tables, but it could in theory be anywhere in the airport.
The interesting thing is that it works a bit differently at LCY, where I had the dubious pleasure of being the lucky pick of the day. There, you have to wait at the BA check in desk for someone to come pick you up, they then take you to some broomstick cupboard of sorts (underneath the main escalator) to interview you for a few seconds and have a cursory search of your hand luggage. Then they take you to the normal security, you cut the queue, but they proceed to a more thorough search of the hand luggage.
The only part that is really annoying is the wait at the check in desk. In my case, it took three phone calls by the check in agent and nearly 30 minutes before the person turned up! The rest was just mildly boring and rather pointless but no issue at all.