Cabinet government before 1916; the creation of the Cabinet Office: the Cabinet Secretariat and the First World War, 1916-18; Maurice Hankey and the interwar years, 1918-39; Edward Bridges and the Second World War, 1938-45; Norman Brook: Commander of the mid-twentieth century, 1946-63; Housing the Cabinet Office, 1916-2016; Burke Trend and John Hunt: adjusting to the modern era, 1963-79; Robert Armstrong and Robin Butler: the last of the traditionalists, 1979-98; New Labour, new challenges: Wilson, Turnbull and O'Donnell, 1997-2010; Coalition and beyond, 2010-16.

Since its creation in the depths of the Great War in December 1916, the Cabinet Office has retained a uniquely central place in the ever-changing political landscape of the last century. While the revolving door of 10 Downing Street admits and ejects its inhabitants every few years, the Cabinet Office remains a constant, supporting and guiding successive Prime Ministers and their governments, regardless of their political leanings, all the while keeping the British state safe, stable and secure. It has been at the centre of everything – wars, intelligence briefings, spy scandals, disputed elections, political crises – and its eleven Cabinet Secretaries, ever at the right hand of their political masters, have borne witness to them all. The true ‘men of secrets’, these individuals are granted access to the meetings that determine the course of history, trusted with the most classified information the state possesses.