My favourite story about security was at a large West London airfield. After a previous scare, Passenger Screening security was enhanced and on the day of a ministerial visit, all the departure level screening positions were open and there were no queues. This was excellent.
The party then went to inspect the arrivals process and promptly, 4 departure positions were closed and the staff were dispatched to Arrivals. Queues quickly built up again whilst Arrivals was smooth and well oiled.
Security at any level is just for show.