LAUSR

This article explores the scope and limitation of the power of the UK prime minister from an institutional perspective. It begins by exploring and confirming the widely recognised tendency towards a more centralised core executive at the heart of the UK government, which dovetails with recent developments in Japan as discussed by Tomohito Shinoda in this special issue. However, the article thereafter argues that this tendency has been constrained once a wider institutional perspective beyond the core executive is adopted. This perspective emphasises the impact of recent constitutional reforms relating to the House of Lords, devolution and the judiciary. These reforms resonate with the idea of a ‘Madisonian turn’ towards greater separation of powers, albeit unintended. Rather than the UK and Japan converging, these institutional changes in the UK narrow the sphere of, and impose constraints on, the authority of the UK parliament and government, which naturally restrict the power of the prime minister.