This chapter examines two closely connected institutions that lie at the epicentre of UK politics and these are the Cabinet and the Prime Minister (PM). The chapter considers the basic characteristics of both. It describes the way in which they operate, including policy, the functions of the Prime Ministerial role, the supporting staff, and the place of both in the UK constitution and system of government. The principle of the collective responsibility of ministers is touched upon. The chapter gives some practical examples of how selective PMs have worked with their Cabinets to demonstrate how these theories can play out in practical terms. The chapter also provides historical material to illuminate the background to the issues it considers. Finally, the chapter asks: is collective government, that is, government by a group rather than a single leader, the right approach for the UK today? The chapter also touches on the issue of Brexit and questions what we have learnt from the Brexit experience in terms of the UK political system.