It is March 2012 and I am in London listening to Susan Cain, who is a phenomenon in the world of current ideas. How influential is she? Well, in the one second it has taken you to read that sentence approximately thirty-two people have viewed her standout talk at TED. And a further 451 have viewed it on YouTube – in the last hour. Her book ‘Quiet’ – ‘The Power Of Introverts In A World That Can’t Stop Talking’ – sits in the New York Times Top Five – and her piece in the New York Times attracted an astonishing 241 comments alone.