‘HOW splendid and honourable it is to meditate on government and public administration – on which our well-being, our health and our life depend – as do all the notable deeds that are performed in this earthly life below!”

So begins the Dialogue on the Government of Florence, written by Francesco Guicciardini in 1524.

A contemporary of Machiavelli, Guiccardini’s Dialogue proposed major constitutional reforms to restore liberty and good governance to his beloved but beleaguered city-state. Florence was then under the corrupt domination of the Medici family – the original populist oligarchs, who turned their vast wealth into personal rule.

The term translated as “government and public administration” is, in the original, “governi publici”. Literally, this means “public government”. Guiccardini stands in the great tradition of “civic republicanism”, according to which the state, in a well-constituted polity, is a public entity [“res publica”].

It belongs to the public.

As Cicero put it a millennium and a half before Gucciardini, “res publica, res populi”: the state is “the people’s thing”.

Public office is a public trust to be used for public ends. Those public ends are determined by public deliberation in public assemblies and councils. Citizens in public life must be faithful stewards of the public good, for which they are responsible to the public.

Guicciardini and his fellow civic republican thinkers contrasted public government with “private government” – government that acts in the private interests of rulers, where the state “is bought and sold for Medici gold”, and where government office is seen as a fiefdom from which to line one’s own pockets.

Policy under “private government” is not made in public assemblies, but in secret, through private contacts, over dinners in the kind of restaurants where those not on the racket cannot afford to eat. Appointments under private government are not made on merit, but by nepotism and clientelism. Everyone serves themselves; no one serves the public.

Today we watch with horror as untraced billions disappear into the coffers of firms with close personal ties to cabinet ministers. We listen with grotesque fascination as Dominic Cummings spills the beans on the chaotic goings on in Downing Street. We roll our eyes when the Prime Minister is said to have missed vital meetings because he is – so we are told – working on a biography of Shakespeare. We glaze over when we discover that his personal debts are paid off by benefactors without him even noticing.

We use words like incompetence, cronyism and corruption, but perhaps we do not realise that all these things are just symptoms of the rise of “private government”.

The institutions, laws, rules, processes, conventions and traditions that once sustained public government have all been kicked aside or allowed to fall into disuse. This started with Tony Blair, whose “modernisation agenda” introduced so-called “sofa-government”: an informal, highly spun, personalised, “Call me, Tony” form of rule. The Cabinet was side-lined. This resulted in the essentially private decision to invade Iraq.

Private rule has accelerated and worsened under Boris Johnson. He despises Parliament, but loves standing on podiums. He strides around on aircraft carriers wearing a pseudo-military uniform like a bargain-bin Trump. He presides like a Florentine despot over a private court. Dominic Cummings held no traditionally recognised constitutional office: he was neither a civil servant nor a minister of the Crown, yet he exercised great influence over the state as a private advisor to the Prime Minister. The Prime Minister’s latest wife is being hailed as “First Lady”, a title unknown to the laws and customs of the realm.

It turns out that all that terribly boring, hidebound, fusty, dusty old stuff was there for a purpose. It publicised power. It made the office, and the duties and responsibilities of the office, bigger than the ego, charisma and appetites of person who happens to fill it.

The constraints against corruption and abuse of power were always subtle, informal, mostly unwritten – but they did work. The British state did develop an honest, efficient, non-partisan bureaucracy and an independent politically neutral judiciary that, for the most part, upheld the rule of law and the rights and liberties of the people. It did practice free elections. The Government was not the Prime Minister’s government: it was Her Majesty’s Government – a little too monarchical for some tastes, perhaps, but a reminder nevertheless that the Prime Minister does not hold office for private gain, but to serve the public interest.

Perhaps the unwritten British Constitution was always an illusion, but so long as people all believed it was real, the illusion was enough. Now those illusions have been shattered. We are left with empty rituals, the meaning of which been forgotten; pomp and vanity, without clear purpose.

We cannot go back to pretending. I have a more splendid and honourable proposal: a proper written constitution to anchor the state in clear and established principles of public government.

Witches in medieval Scotland is the theme of the TNT show at 7pm on Wednesday