I vaguely recall arriving at T4 off a BA long haul flight a number of years ago and as we were so far ahead of schedule, although we had been allowed to land there was some rule/curfew about not being able to use the engines all the way onto the gate stand so we had to be towed on by a tug - remember it was the first (and only) time I've seen them use a tug on arrival rather than departure!