Jonathan Clark was a Fellow of Peterhouse; at Oxford, he was a Fellow of All Souls College; latterly he has been Visiting Professor at the Committee on Social Thought at Chicago, and Hall Distinguished Professor of British History at the University of Kansas. His latest book is a study of Thomas Paine.

As foreshadowed in her Lancaster House speech, Theresa May’s ‘Letter to the Nation’ promises that her 585-page deal would ensure that the UK takes back control of its borders, its money, and its laws. But that is not what the text sets out, as enough analysts have carefully demonstrated. She has therefore placed herself, or has been placed by her advisers, in the position of arguing that night is day, or that a square is a circle. She was already famous for the phrase “nothing has changed”, but her U-turn over financing the care of the elderly was minor compared to this.

Her letter expresses the wish that exit be ‘a moment of renewal and reconciliation for our whole country. It must mark the point when we put aside the labels of “leave” or “remain” for good and we come together again as one people.’ But is this plausible?

It seems more likely that the label BRINO, Brexit In Name Only, will be hung round her neck, just as securely as ‘appeasement’ was hung round the neck of Neville Chamberlain. But any such facile comparison needs careful reconsideration. Chamberlain was an able public servant, as Lord Lexden’s recent short study emphasises, and his rehabilitation is under way. There were far stronger grounds then for thinking that the UK needed time for rearmament than that UK industry now needs time for a transition to a trading relationship still undefined. It was more plausible then to hope that the German problem might be managed than it is now to say that the evolution of a trade association into a United States of Europe with its own army, foreign policy and taxation system is not taking place.

But there are more important differences between the two cases, and they point to far more domestic conflict ahead for the UK today. In the 1930s, the few Westminster politicians who warned of the rise of Nazi Germany won scant reception, preoccupied as public opinion then was by the slaughter of the First World War. Public debate was limited. Now, the choice between Leave and Remain has been fought as an epic ideological battle, as the debate over appeasement in the 1930s never was. Europhiles and Europhobes have set out their cases with economic, constitutional and historical sophistication, and also with effective passion. They have struck a chord, or two chords, in public opinion. Remainers especially see their cause as one that goes to heart of their very beings. Friends, and even families, are divided.

Second, the outbreak of war in 1939 largely ended the debate over appeasement. It created national unity to a remarkable degree. But no such unification is now in prospect. Indeed, the reverse is the case. As the implications of a legally binding exit treaty become evident in practice, the outcry against its terms and its authors could only grow. The future economic relationship between the UK and the EU would be explored in lengthy, and seemingly unending, agonies of negotiation: the UK’s bargaining weakness, as a result of May’s exit deal, would regularly rub salt into these wounds. Appeasement did not break up the Union, although the Irish Republic stood neutral in 1939; in 2018, BRINO would have major implications for Northern Ireland and Scotland. The chorus of mutual blame in the UK could only escalate, and these flames could only be fanned as the 2022 general election approaches.

If this results in a Corbyn victory, the Conservative Party would see a decade or two of introspective recrimination. In the 1997 general election, the Conservatives lost 11.2 per cent of the votes and 178 seats, ending with just 165; a loss on this scale in 2022 is perfectly plausible. One hopes that Tory MPs have their new jobs lined up.

For how long would such turmoil last? Other divisive episodes have occurred in the British past. But for a comparable example of an ideological division among the elite coinciding with passionate division among the people one would have to go back beyond Irish Home Rule or the repeal of the Corn Laws to the Revolution of 1688, when one of the two great parties in the state changed the succession to the throne by a palace coup. As historians now appreciate, it split the nation for decades, arguable until the 1760s. The consequences of BRINO would probably be similar in kind, if unknowable in extent.

Would the consequences be equally shared? The Labour Party seems least likely to be damaged by this issue: the near prospect of ministerial office is the strongest political glue yet invented. But commentators are now reporting confidently on rival groups of Conservative cabinet ministers about to resign if their positions do not win the day. They remind us that there are some situations in life in which a compromise is impossible. In 1939, the UK either went to war with Germany, or it did not. There was no middle course, and there could be no transition period to make possible a middle way.

Then, Chamberlain’s ministry took a decision and Parliament backed it. Now, the ministry has adopted a deal that satisfies neither Leavers nor Remainers. If Parliament nevertheless backs it, the resulting Heath Robinson machine may end in wreckage. The long-term consequences for the standing of the UK’s parliamentarians would then be considerable. Coming after the financial crisis of 2008 and the MPs’ expenses scandal, the institution of Parliament itself will be ripe for reform in a future Labour government.

Is there, even now, a way out? The least bad tactical scenario may prove to be that there is no parliamentary majority for any option. Perhaps a change of Prime Minister will slow things yet further. Time would run out. If so, the UK’s political elite – by its mediocrity, its clumsiness, its self-deception and its careerism – would blunder unintentionally into the best outcome of all, a Brexit on WTO terms. The law of unintended consequences may yet take precedence over human inadequacy.