The writing has been on the walls of Fortune Brands' offices in Illinois for about two months. The conglomerate's confirmation yesterday that it will split up its three business units was clear to see back in October, when hedge fund firm Pershing Square Capital Management announced it had upped its stake in Fortune to 11%. Considering Pershing's previous history of pushing companies to sell off corporate divisions, one can understand that the countdown on Fortune began very soon after Pershing's announcement.