Simple fact is that the exit doors at baggage reclaim have to be a one way system... We used to have security personnel that sat there but they were deemed to be more expensive than the doors they have in now. Also, how could you possibly know that one of the doors was working at "about 10% capacity"? Me thinks it was more along the lines of the British travelling public's fascination with impersonating lemmings, and all simply queueing up at one door instead of using the other 2 that were available. I see it happen all day long.