I'm sure many pax get caught out by the delay at passport control/hand luggage screening...
I arrived at Stansted once with loads of time to spare. As there was NO queue at Passport control I went for breakfast. Twenty mins later the queue was almost out of the door of the terminal. It took ages to get through. Just made the flight ok without holding it up but others wern't so lucky. Perhaps they should make an announcement when the queue reaches say 10 mins?
On one ocassion I arrived two hours before my short haul flight only to find it was delayed for several hours, grrrr. They didn't know which gate it would be when I checked in and the airport _appeared_ to have separate passport control gates for A1-10, B1-10 etc. When it finally appeared on the board I found that channel was closed (heck the whole airport was almost closed)! I had to hunt round to find a member of security staff to let me through. Then as I _ran_ to the gate I was met by irate cabin crew who wanted to know where I had been. I had to reminded them it was they who were late not me.