The Brexit mess reveals something that I have long suspected: that the UK government has no appreciation of constitutional principle. British public lawyers have always been rather proud of the fact that, instead of a written constitution, they have a set of conventions stretching back into hallowed antiquity. Written constitutions are for new-fangled states, like the US – a bit like trainer wheels on a bike. We have the mother of parliaments, thank you very much.

Over 40 years, the EU has become part of the UK constitution in profound ways – it affects the sovereignty of parliament and the structure of the legal system; it is written into the devolution of powers; it underpins the Good Friday agreement in Northern Ireland.

Countries that bother to write their constitutions down include special procedures for changing them. In the US, amendments must be proposed by a two-thirds majority in Congress and ratified by three-quarters of the states. In Canada, a change must be passed by the parliament, the Senate and at least 7 provinces, representing at least 50% of the population. In Australia, changes must be approved by a double majority: a majority of the population, and a majority of the population in a majority of states. I’m simplifying slightly, but you get the idea.

There is a good reason why constitutions are made hard to change. At the constitutional level, you need to take change very seriously. You want the process to take time, so the proposed change is examined on its merits from every possible angle. You want to make sure that there is a broad consensus underlying the change. You want to elevate constitutional matters above the cut and thrust of daily politics. Above all else, you want to avoid casually damaging the constitutional fabric of the state.

What now seems so astonishing about the Brexit referendum is just how casual it was. A hugely complicated issue with profound constitutional implications was reduced to a simple yes/no question, put to the people by simple majority after a brief campaign.

Where was the careful analysis of the constitutional implications – for the legal system, for central government, for devolution and the Northern Ireland peace agreement? (Don’t we have an Attorney-General in this country? Was he on vacation?) Why did no one feel an obligation to define what ‘leave’ actually meant? (If we’d voted, say, to abolish the monarchy, would we have given the public a simple yes/no question without trying to define what Republican Britain looked like?) Where were the special majorities, to protect the rights of the UK’s constituent nations and ensure the decision was based on a genuine consensus?

Ask yourself this: if you set out to design a decision-making process that was guaranteed to be hijacked by demagogues for short-term political ends, could you have done any better than what we just witnessed?

So when they tell you that we need to respect the will of the British people, don’t buy it. There is nothing in constitutional theory or practice around the world to suggest that this was an appropriate way to decide a matter of profound constitutional significance. This was an act of negligence by a government that utterly disregarded its constitutional responsibilities. It should be challenged and resisted.