I had been asked to give a keynote speech at a conference at Columbia University’s Journalism School. It was January 2002. Two planes had been flown into the twin towers of the World Trade Center months earlier and you could still feel how wounded the city felt. You could read it in the faces of New Yorkers you spoke to.

But it was the words of one of his classmates that come back to me now. He had arrived in New York just a few days before 9/11 from his native Pakistan to study at Columbia. He likened the United States to Imperial Rome.

"If you are lucky enough to live within the walls of the Imperial Citadel, which is to say here in the US, you experience American power as something benign. It protects you and your property. It bestows freedom by upholding the rule of law. It is accountable to the people through democratic institutions.

“But if, like me, you live on the Barbarian fringes of Empire, you experience American power as something quite different. It can do anything to you, with impunity… And you can’t stop it or hold it to account.”