I wouldn't be surprised if a large portion of those flying on BA's Concorde flights were frequent travellers upgrading from more mundane classes. The loss of Concorde was surely a blow to them.
Virgin (who I find superior to BA in pretty much ever way) don't even have a First class for Business Class passengers to upgrade to (their "Upper Class" is a merged cabin)
No longer. It appears that very frequent travellers on Virgin now have an option that surpasses even Concorde.