It was offered as a Limited Special Offer from WT on LHR-HKG.
Originally showing as 2200HKD, jumping to 127,000HKD when clicking through.
Limited presumably because the flight is completely full.
I had phoned BA to enquire about the original price and whether any WTP aisle seats were available to make the upgrade worth it for me (the 2200HKD one, about £200, not the other!), but the agent said that no offer should be there as there are no seats left throughout.
So I guess I'll be crammed in my lil WT seat for 12hrs. But at least I'll be £11K richer, eh?