I think it's Swissport. Has happened a few times on my EWG flights outbound BHX. Down the stairs for external boarding only to be held between 5 to 10 minutes on the stairway due to locked door at the bottom. Can't for the life of me understand the logic of that procedure. Last time I was still seated in the lounge and could see the pax standing on the stairs, so stayed put. An irate agent sternly reminded me the flight was boarding. I had to point out that it wasn't!
