The United Kingdom, famously, does not have a written constitution. Rather, our political system has been shaped not by revolution, foreign invasion, or dictatorship but by a series of principles and conventions that have emerged and been tested, then accepted. But one part of that system has never received any detailed scrutiny: The Private Office - the small group of mainly civil servants who support and advise every minister of the Crown from the Prime Minister down to the most junior of ministers. Private Secretaries inevitably have, by dint of their access to ministers and the Prime Minister, massive influence. However, in recent years ministerial pressures for a politicised Private Office have inevitably brought the Civil Service into conflict with recent Governments. With exceptional access to former Prime Ministers and decision-makers Alun Evans describes what Private Office is and why it matters, and - following the egregious constitutional breaches of the Johnson premiership - argues for a reversion to the previous arrangements whereby the Private Office truly can be, once again, the independent junction box of government and a vital part of the British constitution.