He is the heir to a 400-year-old business his family bestowed on him. Shouldn't the moral and ethical priority be to keep such business afloat and bestow it on the next generation in turn? (Not necessarily of his family.)

If that were the case, injecting any real estate windfall in the business would be the right thing to do regardless of his personal ROI. Let the business put to good use the money, which is money the business itself accumulated in hundreds of years looking after the building. Get someone else in charge, be an absentee owner, and let it run.

Of course, if you treat it as a business like any other, such imperative does not exist. That, I think, is where his insistence that he's not a particularly good or interesting person comes from: he knows he's killing a piece of history for his own short-term economic benefit. His insistence that "it's just business" is a way to deflect the moral implications of his actions.

So do it for him. Set up a non profit. Collect the funds necessary to be an absentee owner. Buy the business. Run it for posterity's sake.

If only I had a building to sell in central London...

Enthusiasm for running the business for posterity is probably more important than having a building to sell.

I don't disagree, but I'd probably have more enthusiasm for it if I were sitting on a pile of real-estate cash.