When Mrs. Geordie405 and I checked in on the 31st there were at least 3 agents working, two of whom were dealing with those of us in the Priority queue. We just had to do a document check and show our VeriFLY status before heading to security. It was pretty efficient considering it was New Year’s Eve - although the normal queue was very busy.
We were first in the queue at Gate 3 and took up position at the right hand door. Others “in the know” queued behind us, with those eligible for priority boarding lining up in the direction of the old BA lounge but the queue for regular boarding did stretch all the way back down the corridor.
Gate staff didn’t show up until probably T-20 but it didn’t matter as the plane had been on stand for some time and we boarded immediately. As others have said the normal protocol is that those in Group 1 (at least) would wait by the window and board first.