Attempts to better integrate policy in pursuit of more sustainable development have been made by many countries through the application of ex ante policy appraisal to sectoral policies. The United Kingdom (UK) is often cited as an international leader in this regard, but this is by no means clear. We examine empirically the extent to which the UK Regulatory Impact Assessment (RIA) system facilitates more integrated, and ultimately sustainable, policies. It appears RIA practice is far from integrated. Many RIAs cover a narrow range of impacts, are conducted late in the policy process, have relatively closed consultation processes, do not explicitly show how trade-offs were made, and use analysis inconsistently, if at all. We argue that providing more resources and improving quality control for RIA may improve integration to only a limited degree. More fundamental barriers to integration are hindered by closed policy communities and institutional processes and therefore may be more difficult to overcome.