Defense date: 22 June 2010 ; Examining Board: Kris Deschouwer (Vrije Univ. Brussel), Charlie Jeffery (Univ. Edinburgh), Michael Keating (formerly EUI/Univ. Aberdeen) (Supervisor), Peter Mair (EUI) ; The aim of this thesis is to investigate the relationship between the claims advanced by regional nationalist parties for the re-organisation of state structures based on the recognition of their distinct national groups and the process of territorial restructuring in Great Britain, Spain and Belgium. The objectives are to examine the conditions under which regional nationalist parties have influenced the reform of state structures and to assess the factors that condition the relation between their electoral and policy success. The thrust of the argument advanced is that the influence of regional nationalist parties on the reform of state structures can be understood as the result of processes that take place during the agenda-setting and the decision-making phases. To provoke institutional change, regional nationalist parties must firstly set the political agenda by exerting pressures on mainstream parties in the electoral, parliamentary and governmental arenas. Secondly, institutional change is likely to occur, if nationality claims are accommodated by mainstream parties that are ideologically open to political decentralisation and the recognition of regional nationalism and if the question of territorial autonomy has a broader resonance for political competition between mainstream parties. Finally, institutional change is likely to occur, if the government undertaking reforms is cohesive and there is no ideological opposition by any partisan veto players to those reforms. These arguments are examined through a comparative-historical analysis of political decentralisation in Great Britain, Spain and Belgium, over a time period spanning the late 1960s to the late 1990s. Each case study is disaggregated into time periods that represent moments in the process of territorial restructuring, bounded by significant ...