There will be no red carpet for Adam Curtis when his film "The Power of Nightmares" receives its gala screening at the Cannes Film Festival on Saturday. There would be no point: his film has no leading ladies who could disport themselves in backless numbers or lantern-jawed himbos to vogue fatuously before the snappers. Unless, of course, two of his chief protagonists, Osama bin Laden and Paul Wolfowitz, could be prevailed upon to pose together for the world's press on the Grand Palais steps. Stuart Jeffries speaks to Curtis in The Guardian