Regional autonomy and European integration present national institutions with a double challenge, potentially diluting national authority from both below and above. The interaction between the two processes adds a particular dynamic, as when regions forge direct links to the EU bypassing the nation state. This article looks at three British parties from that perspective, focusing on the autonomy of party branches in Scotland and Wales in relation to their Members of the European Parliament. The empirical analysis confirms that devolution has enhanced the potential for regional autonomy in the parties. However, this has had little practical effect on European policy-making, where national unity prevails. The limited effect of devolution can be explained, first, by the hegemonic status of national party unity and, second, by the disadvantages of operating alone in the European Parliament. An interesting parallel can be drawn to the way subnational authorities relate to EU institutions.Regional autonomy and European integration present national institutions with a double challenge, potentially diluting their authority from both below and above. Britain is an instructive example. Here, the political power of London has been constrained by regionalisation in the form of devolution to the Scottish Parliament and the National Assembly for Wales since 1999. 1 In the same period, policies emanating from the European Union have continued to permeate both national and regional politics (Bache 2008). Devolution implies a new set of opportunity structures at the regional level, changing the terrain in which political parties operate. The research question discussed in this paper is whether devolution has also enabled regional party branches to obtain more autonomy from the state-wide parties in European policy-making. Such autonomy should be visible in enhanced discretion over the selection of candidates and programmes as well as in the forging of direct links to the EU level. British parties are particularly relevant in this regard since Members of the European Parliament (MEPs) since 1999 have been elected on a regional basis, using