Paxing last week ex-LHR T2, following boarding complete and a head count, the Captain informed us that a passenger had boarded that shouldn't have (same operator, different destination and adjoining gate). Everyone had to deplane and return to the gate waiting area to enable a security search. The miscreant had left the aircraft prior to boarding complete (his seat was occupied which required the CC to scrutinise his boarding card and identify the error), but I'm curious as to how he was able to apparently pass through an electronic boarding pass scanner and doc (passport) cross-reference inspection at the gate by Menzies staff? Although his flight was parked on an adjoining stand, the gate heads are not shared so it wasn't a case of taking a wrong turn. This resulted in a 40 min delay and some tight connections at the other end.
My suggestion with gate procedures, better management and more efficient boarding is to ensure that gate PA's are loud enough and clear enough for everyone to hear - I find pre-boarding announcements are often mumbled or indistinct, leading to everyone in the vicinity standing up and congregating near the gate agents. Essentially, as has been said, enforcement of boarding sequence and proper identification of fast-track or priority boarding lanes is required...and a change to hand-baggage allowances.