This chapter examines the major changes which these developments have wrought in British politics, while identifying significant areas of continuity. The standard view of British politics in the twentieth century depicted the United Kingdom (UK) as a highly centralised state in which decision-making authority was concentrated at the centre. The British constitution encouraged this centralisation of power. Government involves decision-making through formal institutions and rules; it is hierarchical, with clear lines of control and accountability. Adherents of the Westminster model held that decision-making power in the executive resided either with the cabinet or, as was increasingly the case in the twentieth century, the prime minister. Organisational change within the civil service has added to the complexity of central government. Constitutional reform and the trend towards governance have brought about significant changes in British politics. The ‘core executive’ model notes that many actors within the core executive possess significant resources, and that no single individual monopolises decision-making.