IT has been another exciting seven days in British constitutional politics as the slow but inexorable unravelling of the unwritten constitution continues.

We have seen inconclusive indicative votes in the House of Commons, the Government’s loss of control of the parliamentary timetable, a private members’ bill rushed through all its Commons stages in one day, another prominent resignation from the Conservative Party, death threats against MPs, violent altercations outside of Parliament and a strongly worded letter to The Times.

Of all of these, bizarrely, the strongly worded letter most clearly revealed the mess we are in.

Submitted in the name of Professor Paul Craig and many other well-respected constitutional academics, it argued that ministers cannot advise the Queen to refuse assent to legislation passed by Parliament.

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This means that the Government would have no way to veto a backbench bill to delay Brexit, such as that sponsored by Yvette Cooper MP. A subsequent letter from Professor Rodney Brazier, published in reply, made the opposite claim.

He argued that the monarch’s duty to act on ministerial advice trumps the convention that royal assent is always given.

We do not yet know which of these interpretations will prevail. It depends on whether the bill passes and how the Government responds. It might ultimately come down to the discretion of the Queen’s Private Secretary – whose actions, one way or the other, will create precedents that shape the convention in future.

This is not the first time a letter to The Times has articulated (or, to put it less discreetly, invented) conventions. In 1950 the question of whether, and in what circumstances, the monarch could refuse a request to dissolve Parliament arose.

The King’s Private Secretary wrote a letter under the pseudonym Senex, setting out the principles under which refusing dissolution would be appropriate. That settled it.

John Drummond of the Constitutional Commission has cogently argued that the so-called British Constitution is “whatever the Government of the day, with a working majority, says it is”.

That is not a bad shorthand. It reflects the fact that a sovereign Parliament can at one stroke, by ordinary legislation, upend all our institutions and strip away all our rights.

It reveals the extent to which we lack the basic constitutional protections against incumbent governing majorities that other countries possess. Yet it only tells half the truth. Conventions can be changed even more simply than that. They are only sustained by political practice. A bold innovation that is asserted and accepted – such as the idea that only the prime minister can advise a dissolution – becomes convention.

A convention that is flouted openly and with impunity ceases, after a time, to be convention. In other words, the rules are what the politicians say they are, except when they are not, in which case different rules apply, unless they don’t.

You wouldn’t run a school chess club or an amateur five-a-side team in such a way, let alone a country.

It does not have to be this way. Elsewhere in Europe and the Commonwealth these things are written down, in the text of a written, supreme law constitution. The Constitution of Saint Lucia says that when a bill is presented for assent, the Governor-General (in the Queen’s name) “shall signify that he assents”. There’s no wiggle room there.

The Constitution of Malta is even clearer; the head of state must grant assent “without delay”. That’s a clear, legitimate constitutional rule that cuts through all this mess.

By putting these rules down in a written constitution, these countries have avoided the uncertainty and muddle that besets the UK. The process of writing down rules also enables choices to be made.

Instead of reading the runes of history in search of precedents on which to hang conventions, the pros and cons of different approaches can be considered in a rational and holistic way, to best realise democratic constitutional principles.

If they want to change the rules for any reason, they can do so by a formal process of constitutional amendment, backed by a broad cross-party consensus, not by letters to newspapers.

The UK is in a constitutional crisis. The Brexit impasse is not the cause, merely a catalyst.

The underlying problem is that Hanoverian-Imperial state, hammered out between the Glorious Revolution of 1689 and the end of the Jacobite wars in 1746, has lost both its rationale and its legitimacy. The constitutional rules, never more than minimally democratic and mostly dependent on the common sense and self-restraint of those in power, have begun to disintegrate. British institutions, once widely celebrated and emulated, are now an international laughing stock.

An independent Scotland, with a new written constitution, could do much better.