It was, we were soon told, "the day that changed everything", the 21st century's defining moment, the watershed by which we would forever divide world history: before, and after, 9/11. Ten years on, much of that early reaction to the day America realised, as New York magazine put it on the fifth anniversary, that "there really are ideological-cum-religious zealots out there intent on slaughtering us in large numbers", now looks exaggerated – albeit understandably. 11 September 2001 didn't change the world for ever.