ONE day in the late 1990s, as I was coming to the end of my time studying Arabic in Egypt, I decided on a whim to travel overland from Alexandria to Istanbul. I had only a shoestring budget, but that did not matter: I was 20-years-old and fully convinced of my own invincibility.

The first stage of the journey, across the Sinai desert to Dahab on the Red Sea coast, is not one I will readily forget. It took 26 bladder-bursting hours, blasted by the wind and sand in the back of an old bus with glassless windows (we were promised “air conditioning”).

As I peered out at the darkening desert, I was reminded of the ancient Hebrews, whose journey took rather longer.

I had often wondered about that. Why did it take so long? According to the Book of Exodus, the Israelites had been liberated from the most unequal and incorporating of Unions. They had dodged the Angel of Death, escaped slavery, fled miraculously across the Red Sea, been sustained by manna and water gushing from cleft rocks and led by a pillar of cloud by day and a pillar of fire by night.

Yet still it took them 40 years to cover a distance that should – even allowing for the climate – only take a few weeks.

One explanation is that the time the Israelites spent in the desert was not just a physical journey, but a legal and institutional one. They had to cross over, not just from Pharaoh’s Land to the Promised Land, but from Pharaoh’s Law to the Law of Moses. They had to shake off the mental and cultural, no less than the physical, shackles of slavery, and prepare themselves to live together in shalom: a justice-rooted peace.

Mount Sinai was a constitution-building moment. In what might be the first constitutional referendum in history, the Law of Moses was not imposed, but accepted by an acclamation of public consent (Exodus 24).

In the same way, modern constitution-building processes usually require the work of negotiating and drafting the constitution to be delegated, by practical necessity, to a few – to a Constitutional Commission or Constituent Assembly. These are the ones who must go, as it were, “up the mountain”. Yet the constitutional covenant cannot be completed without the consent of the people.

It feels like we, too, have been wandering in the wilderness for a long time. The Scottish Parliament opened its doors 22 years ago. In election after election, Pharaoh’s army of blue-rosetted Tories have been drowned in a Yellow Sea of SNP votes. Yet we seem no closer to the Promised Land. Where is the milk and honey? Are we just drifting in the desert, waiting for the Section 30 order to magically appear?

All that wandering around in circles could be excused, if we were any nearer to Mount Sinai. We are not. If anything, we are further away than ever.

From 1977 to about 2005 the SNP had a credible constitutional plan for the establishment of a new Scottish state. It was not perfect. It could be improved upon in all sorts of details, but there was a draft constitution, agreed by the party, publicised, ready to be put before the people for approval in the independence referendum and ready to go into effect – at least as a provisional solution – on the very day when the flags change on Edinburgh Castle.

All that seems to have been abandoned. There is no sign that the current SNP leadership knows what a constitution is, what a constitution does or why a constitution is essential and integral to the case for independence. At best they seem to see it as a “nice to have”, a cherry-on-the-cake that can be delayed until the opportune time.

They have no apparent understanding that independence is a state-building project and that the constitution, as the blueprint and foundation for the state, is the only place to start.

They do not understand how much campaigning traction could be gained by a good constitution, both in mobilising the base of independence supporters and in reassuring wavering Unionists that independence need not be the end of their world.

It is not enough to leave Egypt. Unless we covenant together under a proper constitution, setting clear foundations for democracy, good governance, public ethics and human rights in Scotland, then we will inevitably slip back into old the Pharaonic despotism of “parliamentary sovereignty” and the inscrutable “unwritten constitution”.

If the SNP leadership still believe in independence, they need to show it – now – by doing the preparatory work necessary to bring it about. That means passing a Constitutional Transition Act to establish a Constituent Assembly with clear terms of reference to draft a constitution for an independent state, to be submitted to the people in the next referendum.

Our guest on the TNT show on Wedmesday at 7pm is Yes activist, Iain Leckenby