We have – rather belatedly since it is about to go off air – watched Adam Curtis’s epic historical documentary on the influence of Saudi Arabia and militant Wahabbism on the politics of the west and radical Islam from the moment when the elderly Franklin D. Roosevelt made a deal on oil prices with Prince Faisal.   Curtis claims that the programme, over two hours long and shown only on iPlayer, is intended to make history emotionally compelling through dramatic archival footage and dissonant music, but I was more impressed by its sense of emotionally detached grand narrative, looking at all invasions of Afghanistan as doomed to failure by their landscape and history and by western incomprehension of their society.