Former Egyptian President Hosni Mubarak arrived by helicopter this morning at makeshift Cairo court built specifically for trying him on charges of corruption and ordering the deaths of 800 protesters. Mubarak, who ruled Egypt for nearly 30 years before stepping down after 18 days of protests, pleaded not guilty. The 83-year-old, who has been ill, was wheeled into a cage to face trial with his two sons and other defendants. Thanassis Cambanis, Boston Globe Ideas columnist and the author of “A Privilege to Die: Inside Hezbollah’s Legions and Their Endless War Against Israel,” recently returned from five weeks of reporting in Egypt for a new book he’s writing on the country after Mubarak.