Taxiway B
I cannot understand why the BA 744 was on Taxiway B in the first place, because it serves the domestic terminal apron. Looking at the international terminal apron layout all aircraft ought to taxi straight on to Taxiway A and thence south to 03L or north to 27R.
Someone in ATC must have put the 744 on an oddball routing in to Taxiway B. Was A closed for some reason?