Since you are going LHR-AKL, I presume you are on NZ. I take the NZ flight from LAX often and we are always held back from boarding until the transit passengers are loaded. My last time through was about 4 weeks ago. I'm not exactly sure where they come from, but to the best of my knowledge the only space down the corridor from which they come is a smallish waiting room behind the duty free store in T-2.

It's only an observation but most don't look very happy.

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....airline economics: The only industry where the value of a perishable goes up as the best before date approaches....