What role do individual member states play in the continuing development of European Union (EU) environmental policy? Are they capable of successful intervention in the process of joint rule making to maintain their preferred national policies? On the basis of a detailed analysis of EU environmental pollution control measures adopted in the period 1972-86, some observers have argued forcefully that the United Kingdom (UK) Government successfully defended its sovereignty by systematically manipulating national and European political arenas in order to maintain its pre-existing national policies. However, when other aspects of EU environmental policy are analysed over the full policy cycle, the extent of national control appears much more circumscribed. A comparison of UK Government aims with long-term political outcomes in the sphere of EU biodiversity policy (c. 1970-2000) reveals evidence of firm state control in the short-term, but of significant unintended consequences in the medium to long-term. These findings raise doubts about the explanatory power of intergovernmental accounts of EU environmental policy making.