G4S are a joke. A couple of years back at Wimbledon, one of their guards offered to fight someone once his shift had ended. And then only a few weeks back at Amsterdam Airport(which has security just before the flights), after one of them said to put our boarding passes through the security scanner, they got lost and they really didn't give a **** just shrugging shoulders telling us to get another one when our flight took off in twenty minutes and with it being with easyjet they don't take lightly to that kind of thing. They were found in the end, but I won't forget the attitude of the guards.
Don't get me wrong though, I am sure there are loads of great security staff with G4S, but from my personal experience they do seem to lack consistency with recruits. I could be wrong though and just gone through a couple of bad examples.