Mystery shopper: the elusive West Ham investor Daniel Křetínský

Czech billionaire has also invested in Royal Mail, Sainsbury's, a French newspaper and UK power plants

Daniel Ketinsky has made a fortune snapping up leftovers from the old economy. The Czech billionaire owns a clutch of coal companies, and in recent years he has made waves with investments in pillars of the old economy such as high street retailers, supermarkets and newspapers.

Ketinsky holds his cards so close to his chest that he gained the moniker of the Czech Sphinx" from a Polish magazine. The nickname has stuck, but the businessman's profile outside his homeland has grown after a spree of acquisitions.