Warren Buffett, the world’s most famous investor, spent £480m buying Tesco shares following its profit warning earlier this year. After months of the shares going nowhere, he is now sitting on gains of almost £30m.A day after Tesco’s January warning, Mr Buffett upped his stake in the retailer to 5.08pc from 3.21pc. He obviously took the view that the group’s short-term difficulties would not impact long-term cash generation, dividend growth and capital discipline. As a value investor, he took a long-term view.