This book analyses the role of evidence in taking wellbeing from an issue that has government attention to one that leads to significant policy change. In doing so, it draws on contributions from political science, policy theory and literature specifically on the evidence and policy relationship. The book has three main aims: to understand the role of evidence in shaping the prospects for wellbeing in public policy; to inform the barriers literature on the use of evidence in policy; and, to inform the multiple streams approach (MSA) to agenda-setting. While the book focuses on developments at UK government level, a number of the findings and arguments presented here have wider significance, both in relation to wellbeing developments elsewhere and to the theoretical literatures on agenda-setting and evidence use. The book draws on insights from interviews with policy-makers and stakeholders that were undertaken as part of the work of the Community Wellbeing Evidence Programme of the What Works Centre for Wellbeing.