The phrase "constitutional crisis" looms large over the aftermath of Britain's vote to leave the European Union. The possibility of such a crisis has already been invoked in connection with what would happen if the Scottish Parliament refuses to approve Britain's withdrawal from the EU; what might happen if Britain's main Parliament should ignore the results of the Brexit referendum; and the possible consequences of taking seriously the popular petition calling for a second vote on the basis of a new "rule" requiring a 60 per cent approval and 75 per cent turnout on EU-related matters.

All this talk raises an inevitable question: What, exactly, is a constitutional crisis? And equally fascinating, what would a constitutional crisis look like in the country that initiated the modern idea of the national Constitution and yet still lacks a written one?

There is no official definition of a constitutional crisis - that in itself is a telling fact. In order to trigger one, a country usually has to be facing a situation in which its constitutional principles offer no clear, definitive answer to a pressing problem of governance.

Although constitutional uncertainty is a necessary condition for a crisis, it isn't sufficient. For a situation to count as a crisis, powerful political actors, which can include large swathes of the population, have to signal that they are ready to press one course of action to its limits. Meanwhile, other comparably powerful actors have to be prepared to push the other way.

Thus, for example, there was no definitive answer to what should happen when Florida's courts ordered the disputed 2000 electoral recount to continue, as requested by Democratic presidential candidate Al Gore, while Florida's Secretary of State Katherine Harris was asserting that she would send presidential electors based on the initial vote tallies favoured by Republican George W. Bush.

The election could have been thrown into Congress, which might have resolved the conflict between two competing Florida delegations of electors. Or the US Supreme Court could weigh in, making a new law and deciding the issue, as indeed it did.

But the uncertainty didn't lead to a constitutional crisis because Mr Gore conceded, recognising the authority of the federal court. If he had argued that the whole issue was outside the court's jurisdiction - an entirely reasonable claim in terms of constitutional law - and if a good part of the Democratic Party had backed him, that would have counted as a genuine crisis. The Supreme Court's Bush v Gore decision was constitutionally terrible. But the court's legitimacy successfully averted a constitutional crisis.

In the United States, as in most countries, uncertainty arises when the written document that everyone agrees is the Constitution doesn't clearly resolve an important conflict.

But that model doesn't work as clearly in the United Kingdom. The first modern emergence of the term "Constitution" to describe the rules and principles governing the deployment of public power took place in England in the 17th and 18th centuries. The definition from the time that I like most is that of Henry St John, First Viscount Bolingbroke, writing in 1733: By Constitution we mean... That assemblage of laws, institutions and customs, derived from certain fixed principles of reason, directed to certain fixed objects of public good, that compose the general system, according to which the community hath agreed to be governed.

Notice that Bolingbroke speaks of an "assemblage". Britain then did not have a single written document that could be identified as its Constitution, with a capital C.

It still doesn't. Consequently, the British Constitution remains an assemblage of written laws, institutions such as Parliament, customary practices, and perhaps most importantly, ideas - Bolingbroke's "principles of reason" - that are shared and argued about by various constitutional actors.

For the most part, the British Constitution has worked well. That's why, even after the 1787 Philadelphia convention proposed the first written national Constitution, and after almost every country in the world has adopted a written Constitution during the past century, Britain remains as an outlier.

It could be argued that the unwritten nature of the British Constitution increases uncertainty, making a crisis over Brexit more likely than it would be if Britain had a written Constitution.

Thus, for example, technically, the leave referendum wasn't binding on Parliament. In a country with a written Constitution such as the US, it might be easier for the legislature to ignore a non-binding referendum. But the unwritten constitutional principle of democracy would make it problematic for Parliament to do so, because it would be contradicting the expressed will of the public.

The role of Scotland's Parliament in a leave vote is also made more complex by the absence of a unifying British constitutional document. A House of Lords report on Brexit quotes Sir David Edward, a former judge on the European Court of Justice, saying that in his opinion, the Scottish Parliament would have to give its consent to withdrawal, because the Scotland Act of 1998 binds the Scottish Parliament to follow EU law.

The Scotland Act is an act of Britain's Parliament, and according to one powerful British constitutional tradition, Parliament's supremacy is supposed to be absolute. In theory, Parliament could amend the Scotland Act so that the Scottish Parliament would no longer have to consent to Brexit. Yet it's unclear whether that act would itself precipitate a crisis, since it would so obviously slight the sovereignty of Scotland. Alternatively, there might be a crisis if Britain announced it was leaving the EU and Scotland announced that it had vetoed the process.

Yet it's also worth remembering that Britain has the longest tradition in the world of resolving its potential constitutional confrontations relatively smoothly, without a written document. That tradition would tend to suggest that regardless of the current uncertainty, Britain will manage to avoid a constitutional crisis in settling the questions around Brexit. In the end, I would bet on the tradition of flexibility and consensus. Britain may have made a disastrous choice. But constitutionally, it will muddle through - ideally with no more referendums.

BLOOMBERG VIEW