Have you ever wondered what happens behind the scenes in the corridors of power during a major crisis or after a ministerial reshuffle? How do new government ministers get to grips with their portfolios and priorities? Who guides and supports them? And why, sometimes – during events such as 'Partygate' – do things go wrong?

In this meticulously researched book, former senior civil servant Alun Evans lifts the lid on a vital but little-known cog in the machinery of government: private office and the private secretaries who work within it.

Private secretaries exercise huge influence, and yet most of us have never heard of them. They are the ones who manage the flow of work, who whisper quietly in ministers' ears and who have been Prime Ministers' closest, most trusted and most discreet confidants. At critical moments in our national history – from the Falklands War to the Westland affair, from Black Wednesday to the 2008 financial crash, from New Labour to the coalition government – they have been central but hidden players.

With exceptional access to former Prime Ministers and decision-makers, Evans explores what private office is and why it matters to British democracy. He argues that following the egregious constitutional breaches of Boris Johnson's premiership, private office must once again be taken seriously so it can return to being the independent junction box of government and a vital part of the British constitution.