David Cameron’s autobiography is being serialised in The Times in the UK in recent days and the focus of the media has been on his unflattering comments about his Brexiter colleagues, including current UK prime minister Boris Johnson.

In the book, Cameron claims Johnson is a liar who never really believed in Brexit, but Cameron will go down in history as the man who pressed the button for the 2016 referendum – and not for his character sketches of his colleagues.

One consequence of the 2016 outcome is a constitutional crisis, with regular trips to the courts in order to resolve disputes about the powers of parliament over the executive.

One such case is being heard this week, about the suspension of parliament by Johnson, appealed to the Supreme Court by the government after a court in Scotland deemed it to be unlawful.

A contrary finding from an English court, which declined jurisdiction, is being appealed simultaneously by the plaintiffs, a group which includes politicians opposed to Brexit.

If Johnson persists in disobeying parliament, there will be another excursion to the courts next month

Prior to suspension, parliament passed a law – which Johnson proposes to ignore – requiring him to seek a further delay to the UK’s withdrawal from the European Union if a deal is not agreed before the 31 October exit date.

If Johnson persists in disobeying parliament, there will be another excursion to the courts next month, but this matter is distinct from this week’s case, which is concerned solely with the legality of the prorogation or suspension of parliament.

Constitutional uncertainty

The source of this constitutional uncertainty is straightforward.

The 2016 referendum was only the third national plebiscite in the history of the UK and the first where the electorate voted for change.

Back in 1975, the Labour government of Harold Wilson held a poll which confirmed the UK’s membership of what was then the European Economic Community by a 2:1 margin, so no action was required of government.

In 2011, there was again a 2:1 margin to leave the electoral system unchanged.

But in 2016 the electorate voted narrowly for change, to quit the European Union, sparking a constitutional as well as a political crisis which has yet to play out.

The UK does not have a codified constitution, one of only three countries in the world without one

The crisis is constitutional as well as political in the sense that it has raised issues about the respective roles of the organs of state – parliament, the executive, the courts and indeed the crown.

The UK does not have a codified constitution, one of only three countries in the world without one (the others being Israel and New Zealand).

Instead, a mixture of legislation, precedent and convention comprises the constitutional order, and the sovereignty of parliament is the core presumption, hence the current succession of court challenges to the actions of the executive.

In Ireland, referendums are held only for the purpose of amending the written constitution.

There has never been a consultative referendum in Ireland, and the 40 plebiscites held since the 1937 constitution was adopted have in each case been decisive.

On 29 occasions the voters approved the change proposed and on 11 occasions they declined to do so.

But there has never been a post-referendum row about the will of the people along the lines of Brexit.

The 2016 UK referendum was the first in UK history where the electorate voted for change

Irish referenda are final, and the plebiscite has already been implemented (the constitution altered or left intact) when the returning officer sits down.

The 2016 UK referendum was the first in UK history where the electorate voted for change, and crucially it was not merely consultative, it was vague in its implications.

The change option won a narrow majority but the instruction to leave the EU is open to multiple interpretations, unlike remain, which requires no action by government or parliament.

There are numerous alternative courses of action which would satisfy the instruction to leave, ranging from a continuing close relationship with the customs union, the single market, or both, to the disruptive no-deal crash-out favoured by ultra Brexiteers.

Whatever way Brexit plays out, the events of the last few years have stimulated a debate in the UK

Remainers complain that the no-deal option was not on the ballot and they are quite correct, but neither was any other specific form of departure.

Whatever way Brexit plays out, the events of the last few years have stimulated a debate in the UK about the unwritten (strictly, it is better described as uncodified) constitution.

When the dust settles, there may well be a Royal Commission to sort things out.

Back in 1975, Margaret Thatcher, then the leader of the opposition, objected to Harold Wilson’s first-ever resort to the referendum device – she thought it would conflict with the sovereignty of parliament.

It did not on that occasion, or on its second outing in 2011, since the electorate chose the no-change option.

But Thatcher’s prescience should now be acknowledged. It is very awkward to find a place for the cuckoo of referenda in the nest of a system built around a sovereign parliament.

Cameron’s accidental legacy could be a new constitution.