This thesis examines the political and social responses of the Anglo-Norman aristocracy between 1087 and 1106 to the issue of divided lordship. The central theme is the importance of the concept of political legitimacy in shaping the political culture and actions of the aristocracy during this period. The exclusion of significant sections of the cross-Channel aristocracy from the consultation process in selecting a king in 1087 and 1100, ran contrary to the accepted political norms and created doubts over the legitimacy of Rufus’ and Henry I’s regimes that could be revived at moments of crisis. This found expression in the support given to Robert Curthose’s challenge for the English throne in 1088 and 1101, but also in open rebellion in 1095. However, the limitations of violence as a means of effecting long-term change necessitated a search for a negotiated political settlement that would open the way for Normandy and England to enjoy co-existence as a permanent solution to the problem of divided lordship. This approach locates the Anglo-Norman aristocracy firmly within the recent scholarship of the early and late medieval aristocracy, where political discourse is analysed primarily in terms of succession and legitimacy. Therefore, at the centre of this analysis are the contemporary and near-contemporary narrative sources, which display a firm understanding of contemporary theories of kingship and the politics. When brought into focus with charter evidence, specific aspects of the wider socio-political culture of the aristocracy, in particular religious patronage, marital strategies and inheritance patterns, can then be read as both responses to the wider question of the succession, and also as a commentary on contemporary politics.