Sarah Montague speaks to economist Professor Sir Paul Collier. The refugee crisis is one of the world's most intractable problems: 60 million people have fled their homes, with a third of them also fleeingtheir own country. But Professor Collier believes the problem is fixable and 'we can do it easily'. The solution, he argues, is to give refugees jobs. In doing so he suggests everyone will benefit. But if the answer is so simple, why has it not been done before?