While Britain's heritage officials decide whether to nominate more sights for World Heritage status, Emily Maitlis asks if the UN's heritage police is a force for good, protecting our cities against greedy developers, or if it is stopping the flow of modern life? Should the notion of a global heritage be allowed to override local democracy? What can this organisation do for sites that have been shattered by conflict or decimated by industry? Has heritage's equivalent to a Michelin star lost its integrity on the world stage?