This chapter assesses the nature and purpose of constitutional conventions. The discussions cover the concepts of collective and individual ministerial responsibility; the relationship between the Monarch and her Ministers; the relationship between convention, statute, and the common law; the Matrix-Churchill controversy; the ‘Ponsonby rule’ and the Constitutional Reform and Governance Act 2010. It is argued that the concentration of effective political power is often very intense, even within a political party; small groups of senior Ministers or even the Prime Minister alone may occasionally be, to all intents and purposes, ‘elected dictators’.