Owner: Lakshmi Mittal, worth $16.5 billion
Purchase Price: 117 million pounds ($222 million at the time) in 2008
The steel magnate is believed to own three homes on the high-security street known as Billionaires Row, including a neo-Georgian mansion near the Israeli embassy. The home (not pictured), rumored to have been purchased for Mittal's son, was sold by hedge fund billionaire Noam Gottesman.