Group boarding two experiences.
Monday morning LHR T5 to Paris. For some reason a number of group 1s decided they needed to queue - quite bizarre. Call to line up and board. Lots of preboarders (disneyland paris) then group 1, other groups being called to stand in line. No issues given the flight was absolutely full. About 10 group 1, 30 group 2,3
Tuesday evening Paris to LHR T5. Sauntered down from Cathay lounge to gate 45 when boarding called. Fair number of people people milling about at the gate, passenger service agent when asked quite clearly said "we are boarding group 1 only at the moment". Walked straight up to the desk and onto the plane.
All the staff seemed well organised. Due to my own boarding group didn't see anyone sent back on the walk of shame...