I was told (by BA ground staff) that internally and informally, the Concorde door is referred to as the 'million pound door', as BA have to pay an extortionate amount to BAA to have that door and not have F class pax walk past the shops.
Pretty much true. When T5 was being designed, the briefed BA requirement for the Galleries was for entrance at the same level as security. BAA disregarded this, and provided the entrance on the gate level as they wanted the BA premium customers with lots of cash (in their eyes) to walk past all the shops. That is why its all the posh shops going down that end towards the Galleries. On many occasions before opening BAA were approached again and asked if they would reconsider. Sometimes the answer was a flat no. Sometimes they said yes, but with a hefty price tag. And a million£per year is underestimating it by a long way. Eventually they agreed to having "the million pound door" but on the proviso that it really was only for use into the Concorde Lounge so they don't lose too much shopping revenue. And again a million £ price tag is a bit stingy as an estimate of what that is costing.