There’s more billionaires in the world now than ever before. And as wealth is concentrated into the hands of a small group of people, the power of those select few is also growing – particularly in the US, where billionaires have been getting more and more access to Donald Trump. The journalist Evan Osnos tells Matt Galloway about the influence and excesses of the .01%, which he charts in his new book, The Haves and the Have Yachts.