Are the Super-Rich killing global cities?

Are our big cities turning into ghost towns? The super-rich from the Middle East and Russia are buying up prime real estate around the world as a safe investment for their money. But with nobody actually living in the properties, there's an eerie deserted feel about town. We hear from Stephen Sobey, who has a flat in the affluent Knightsbridge district of London, and from Roger Bootle, of Capital Economics.