Whatever happens, if anything happens, on 31st October 2019, the fall-out from the agonising process of UK withdrawal from the EU will remain, like the aftermath of the countless wars that have littered British history. The country will be different, and we will have to learn to live with the difference, as we have done so often before.

The British economy will be one area of post-war reconstruction. Another will be our inescapable involvement with an EU, already fragile, but now damaged, perhaps terminally. A third will be the threat to the unity of the United Kingdom and the unsettling of the future of Ireland. We assume that we will muddle through these challenges, as we seem to have muddled through so much in our past.

British society is already profoundly different from the society that we were, in which a ruling class of dubious personal merit, that had somehow absorbed the middle class in the 19th century, worked fairly efficiently within the muddling-through formerly known as liberal democracy. Populism is not an adequate term to describe the revolution in self-government of recent years, led by the so-called social media.

The firm foundation of liberal democracy was the rule of law. UK withdrawal from the EU raised legal problems of unprecedented complexity, and not only those relating to the separation of the powers of government. The shocking disregard of law in the governmental management of UK withdrawal will haunt us for years to come.

It is even possible that the legality of a so-called no-deal Brexit could be challenged retrospectively in the UK courts, the constitutional courts of other member states, the European Court and in many international courts, including the International Court of Justice. Whether or not, in the end, we remain in the EU, there must be a return to strict legality over the coming years. I myself was at one time a lawyer in government service. I know that it is the job of government legal advisers to speak law to power. Courts are not there to interfere in political life. They make successful political life possible.

Most troubling of all the challenges facing this country is the state of the world into which we are now moving. Three of the pillars on which the brilliant post-1945 resettlement of the world rested are now at risk.

The end of the American Century is the beginning of a new kind of international diplomatic anarchy. The idea of natural and inevitable social and economic progress is hard to sustain, not least in the face of seemingly ineradicable social and economic inequality. The security blanket of large-scale ideologies that characterised the Cold War period is being replaced by a post-truth chaos of ideas.

There are activists who see all this, and will not keep quiet. But it is not surprising if most people are tempted by fatalism and defeatism. The problems are simply too great to comprehend, let alone to manage. Human progress, such as it has been over recent centuries, and it has been almost miraculous, has depended on boundless human energy and invincible human hope. If our younger generations cannot find those things within themselves, those of us who are relics from a different past will depart from the world in terrible sadness.

Philip Allott is Professor Emeritus of International Public Law at Cambridge University and a Fellow of Trinity College Cambridge