The breathtaking images seared into the mind of the world five years ago today retain all their power to haunt us. That moment when objects as normal as civil airliners were turned into rockets that brought down the landmarks of a great city won a unique place in the annals of infamy. Even at this distance, the moments of impact, the collapse of the towers, the smoke and dust billowing out of Manhattan are pitiful and raw.

Whether that monstrous master-stroke of jihadi terrorism "changed the world" still depends on the sort of response that the many in the world who stand by tolerance and the rule of law make to the few who wish to trigger a clash of civilisations separating Muslim from Christian and Jew.