The economist Sir Paul Collier has spent much of his career thinking about some of the biggest challenges we face around the world – and then trying to find solutions for them. He’s focused on low-income countries, particularly in Africa, looking at why they haven’t benefitted from the forces of globalisation. He’s examined the causes and the consequences of civil war, and the role of foreign aid. He received a knighthood in 2014 for his work on Africa.