The centre of central government comprises three sets of institutions: the Prime Minister’s Office based at 10 Downing Street; the Cabinet Office at 70 Whitehall, and HM Treasury at Great George Street. Together they form what some political scientists have called “the core executive”. How these key institutions operate is of first importance for the overall performance of decision-making across central government as a whole. We first review the modern history of these bodies, beginning in 1968. (For an overview of the longer term picture, see also the Annex which sketches the UK core executive from the first appearance of the Prime Minister role in the 1720s up to the 1960s). Next we analyse the key recurring questions that surround the ce...