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So there are limits to the magician's powers. For a ­moment there, when the footage from Tehran showed young women wearing Victoria Beckham sunglasses, peroxide hair poking from their hijabs, lining up to cast their votes in a record turnout election, it looked as if Iran was about to end the sullen estrangement of the last four years, turf out Mahmoud ­Ahmadinejad and present a new, more open face to the world. If that had been the outcome of Iran's election, it would have been notched up, in part, as an early triumph for Barack Obama: his ­allies would have declared that the hand the president stretched out to the Muslim world in Cairo less than a fortnight ago had...