Azakhman
What most likely happened:-
(1) Unusually short flight time (mine yesterday only 11:30) meant a delay due LHR curfew.
(2) Crew held in CX City. Crew channel closes, thus crew go to aircraft via terminal.
(3) Delay triggers refreshment voucher claim for all crew - redeemable in the only airport outlet still open - Starbuck's
(4) Ground staff blame everything on those nasty crew members.