not nationality but residency
doesn't that happen anyway?
It's priority for local residents, but some 'tourists' seem stay for quite a while. Lots of H customers have multiple passports/citizenship and homes, H doesn't seem to care until they need to or it's brought to their attention.
A longterm London customer (of whatever nationality) will always be given priority to someone flying in to London (of whatever nationality) with the sole aim of securing a bag. Most don't anyway since London is 20% VAT and in Paris (non-Euro) customers can get some money back.
I don't think people realise how busy London H stores are currently. It's hard enough just to see a bag/leather specialist and most wish-lists are quietly forgotten about unless there's a request for a HAC 50 or Travel Bolide.