Contributor(s): Tim Marshall | Foreign Affairs Broadcaster and Journalist, Tim Marshall, author of new book Prisoners of Geography explains how decisions made by world leaders are constrained by geography. It is true that to understand world events (such as President Putin's invasion of Crimea and events in the Middle East), you need to understand people, ideas and movements… but if you don’t know geography, you’ll never have the full picture. Tim Marshall (@itwitius), journalist, writer and broadcaster, is best known for his reporting and analysis of events in the world of foreign affairs and international diplomacy. Whilst at Sky News, Marshall covered twelve wars over a twenty-four year period. He is the founder and editor of 'thewhatandthewhy.com', a web platform for journalists, politicians and students to share their views on world events. Charlie Beckett (@CharlieBeckett) is the founding director of POLIS, the think-tank for research and debate in to international journalism and society in the Media and Communications Department.