Originally Posted by
UKtravelbear
IIRC there is a passport check after you get off the bus but before you enter security - it’s basically do you have one and a quick look but not immigration,
There should not be any passport check for a normal airside transfer - if you witnessed it happening that was for a targeted reason (perhaps for a passenger's nationality requiring a transit visa, for example). In that case I would expect a Border Force officer to be at the door of the incoming flight, not after the bus journey.