To some, the UK’s unwritten constitution is an invitation to abuse, and Brexit has put it under strain. But Philip Allott (University of Cambridge) argues that its ability to evolve over centuries is a source of strength, and means that violent constitutional change is not necessary.

Three things can be said of all human societies, from the family to the international state-system. The first is that they are in a state of permanent organic change, whether or not they have a written constitution. The second is that social change is a form of evolutionary adaptation to changing circumstances, designed to secure the survival and prosperity of the society. The third is that the changing circumstances include a permanent struggle among the holders of political and economic power within the society, mainly inspired by self-interest, but which the formal structures of the society are designed to reconcile, with a view to serving the common interest of its survival and prosperity.

Even in a society with a written constitution, there is a penumbral unwritten constitution formed from its day-to-day implementation, containing a mass of practices and interpretations filling the gaps between the written words. Breaks in the organic evolution of a society may be caused by events on a spectrum ranging from pressure for structural change (reform of the franchise in 1832; reform of the House of Lords in 1911) to revolutions involving the use of force.

A revolution, which the Romans called ‘a new order of things’, often claims to be the restoration of an old order. The makers of the American Revolution invoked ‘the rights and liberties of the English people’ that they had inherited from Anglo-Saxon England. The deposing of Richard II in 1399, the judicial assassination of Charles I in 1649, and the so-called ‘vacation’ of the throne by James II in 1688 were all presented as the restoration of an order that had been violated. There can even be an element of constitutional nostalgia in violent revolutions.

When the clans of families in ancient Greece formed themselves into city-states, observers – not least Aristotle – noticed that the central challenge of organising such a society is the distribution of public power among those who make the law, those who apply the law, and those who enforce the law: that is to say, the powers and functions that we call legislative, executive and judicial. Aristotle also noticed that the extremes of tyranny and oligarchy and democracy are natural threats to the well-being of such a society, if the balance of public powers in not well managed in practice.

The written constitutions of the modern world are structured around such a distribution of public power, even if they are also capable of being used as the legal justification of otherwise highly undesirable societies. Like Athens and Republican Rome, we in the UK do not have a written constitution. This means that the distribution of the three forms of public power is the product of evolutionary constitutionalism. The interaction between our internal politics over the course of fifteen centuries and the formation of an unwritten constitution of enormous subtlety and complexity and flexibility should be seen as a wonder of the world.

It also means that each generation has a responsibility that goes beyond politics. We are guardians of what we have inherited. Edmund Burke said that we should comprehend the British constitution so far as we are able and, thereafter, we should venerate it. In particular, we must never cease to watch the evolving relationship between the legislative, executive and judicial organs of the constitution. After 1832, Parliament became a great engine of social change. The Duke of Wellington called it revolution by process of law. Engels called it the most revolutionary body in Europe. We avoided the violent constitutional changes suffered by so many other European countries.

Government, not least local government, became a highly efficient system of social organisation. The courts, which social critics – not to mention novelists – had presented as havens of an obscure abuse of power, were reformed and acquired great prestige. In the 20th century, a remarkable but not unforeseeable form of constitutional evolution took place. The organisation of a massively increased economy, and the management of wars, put immense power into the hands of central government, at the expense of Parliament. Lord Hewart called it ‘the new despotism’ (1929). Lord Hailsham called it ‘elective dictatorship’ (1976).

People speak of the sovereignty of Parliament. That is misleading. Parliament has three crucial functions as the central organ of representative democracy, alongside the executive and judicial branches of government, in a complex confusion and separation of powers, all of them subject to the Rule of Law as the ultimate principle of our constitution. Parliament’s legislative acts override the common law. It calls the government to account through the two constitutional conventions of ministerial responsibility and collective Cabinet responsibility. It is what Churchill called the grand forum of the nation.

The political struggle surrounding the question of Brexit can be seen as yet another of the countless great constitutional struggles of our long history. Ironically and painfully, it might even be welcomed as a struggle about a redistribution of ultimate public power. The House of Commons has known great times over the course of the centuries. The Rule of Law enforced by the courts has been the guarantor of constitutional order. The executive branch of our government has been as good as any in the world since Anglo-Saxon times.

To live under an unwritten constitution is to live in hope, knowing that change for the better is possible and that violent constitutional change is not necessary.

This post represents the views of the author and not those of the Brexit blog, nor LSE.