The United Kingdom is in a constitutional impasse. The government cannot command a majority in parliament to separate from the European Union’s constitutional order, even though it has for three years been trying to do scarcely anything else. Meanwhile, parliament has been unwilling either to bring the government down or reboot EU membership.

Underneath the melodramatic uncertainty lies, I think, a deeper trouble. The UK’s constitution is supposed to work as an ongoing reflection on history. This imperative doesn’t prevent constitutional change: it makes such change a good deal easier than many constitutional polities do. But it does demand historical knowledge of the country’s laws and customs. Determining what might be prudent adaptation to changing circumstances, and what risks wreaking unintended havoc, has to be a matter of judgement about the long journey from the past to the present.

For nearly five decades such historical reflection has been in short supply at Westminster. In pushing EC membership the Heath government should have reckoned with parliament’s legislative sovereignty, not assumed that it was dispensable if there were an economic gain to be realised. In pushing asymmetrical devolution for Scotland and Wales, the Blair government should have remembered that Home Rule for Ireland proved so politically difficult partly because nobody could figure out how to achieve it without producing discontent about England’s representation in parliament. Instead, these governments wished to be rid of historical constitutional burdens without dismantling the constitution that fashioned them.

Tony Blair, in particular, appeared to make evicting the past his primary political project. He wanted, he proclaimed, Britain to be a “young country”, before proceeding to exercise with some abandon the power cumulatively established by the constitutional moments of 1689 (Bill of Rights), 1832 (First Reform Act) and 1911 (Parliament Act, to restrict the power of the House of Lords).

Run by politicians lacking the historical sensibility to guide it, the constitution has been hollowed out. It is easy to dissect the ensuing political problems and proclaim that the constitution has become consequently too incoherent and divisive for purpose. But this judgement oversimplifies the present constitutional predicament. The UK’s constitution has long been politically fraught and in good part must be. If constitutions are supposed to be a source of unity to contain democratic conflicts, Britain’s unwritten constitution appears never to have been one at all. In origin it is an English constitution into which Wales, Scotland and Ireland were incorporated before the majority of Ireland seceded. It has allowed any number of messy and unsteady arrangements about religious, legal and educational autonomy, and it has created sustained historical episodes of parliamentary paralysis around the Union.

The constitution’s adaptability has also fed off past historical conflict that was never resolved; 1689 was not simply a fierce dispute about the rights of parliament in relation to the Crown. It was a political argument about 1066 and whether the Conquest represented a constitutional rupture. Over the next century, even those who made parliament’s rights the constitution’s centre continued to disagree over whether the Bill of Rights restored the tenets of the “ancient” constitution manifested in Magna Carta, or was an act of creation. Radical political movements frequently drew from the same indeterminate imaginative historical well as their opponents. The Levellers and the Chartists overtly appealed to the past. For them, retelling England’s constitutional history going back to the Conquest was indispensable to their insistence on the right to vote.

Today, it is not conflict about what the constitution means, or the constitution’s contradictions, that threatens the constitution. It is the weak capacity for serious imaginative conflict between MPs about constitutional history to make arguments about how politically to act. The near absence of British history from much school education for several decades might be seen in this respect as an act of constitutional vandalism.

Yet neither can the constitution be consigned to history. Many voters might not have been taught much British history, but the national past has been absorbed in local traditions, place names and memorials, its continuities are represented by a still popular monarchy, and they are writ across the island’s landscape. Brexit is a part conscious and part inchoate insistence among a significant section of the electorate that the English and Welsh, at least, are still a national people because, as a consequence of a shared and contested past, they possess a constitutional heritage that, having been forsaken, should now be restored.

But without awareness of English and British political history, Brexit does not seem like a constitutional issue at all. This incomprehension is why it appears much easier for some critics to imagine that Leave voters are nostalgic for empire than to recognise that they might consider easily lost democratic liberties to be their birthright. Even when its history is recognised, this political story lacks legitimacy for those who see little of meaning in the idea that English or British history can yield distinctive or coherent political identities in the present.

The constitutional past cannot unite us, but neither, so far as the Union is concerned, can a new written constitution. We still carry the political responsibility to learn the United Kingdom’s history.

Helen Thompson is professor of political economy at Cambridge University and a regular on the Talking Politics podcast