IN 2014, the door to independence was wide open – but we stood on the threshold like an indecisive cat and refused to walk through it.

About 55% of the Scottish electorate – and especially its older and richer segments – took the view that independence was too risky. Iceberg or no iceberg, they wanted to stay on board the SS Britannia, not scramble for the untested lifeboats of independence.

The independence movement accepted that result with relatively good grace. There was a political backlash, sure, with a surge in the SNP’s membership and a landslide victory in the 2015 general election.

But there were no ­riots, boycotts, or moves to delegitimise the result.

READ MORE: Tick-boxes and toothless commissions reveal crofting truths

Despite the skewed media landscape, which did so much to damage people’s trust in the BBC, the overwhelming majority of us accepted that we lost (more or less) fair and square.

That did not mean that the argument for ­independence was over. It was settled for now, not forever. “How long” was an open ­question. Some said it was a “once-in-a-generation” ­decision. It might be argued that a political ­generation is shorter than a biological one.

A few electoral cycles can bring about a ­profound change in politics. In Northern Ireland, the right to a referendum recurs every seven years; ­according to that reasonable measure, we should have had another in 2021. Alternatively, one might consider a generation to be 20 years (Thomas Jefferson certainly thought so). If so, we are now just 10 years from another.

The 2014 result also did not mean the end of Scottish popular sovereignty as articulated in the Claim of Right for Scotland – the sovereign right of the people of Scotland to determine the form of government best suited to our needs was not surrendered by the decision to maintain the Union. It was simply decided that we would exercise that sovereignty, for the time being, in some form short of independence.

READ MORE: Stewart McDonald: We are living in the early days of a new world

The supporters of “The Vow” promised that voting “no” to independence was not a vote for the status quo. In broad but vague terms, a new, reformed Union – something better than both devolution and independence.

The Smith Commission was duly established, and its feeble recommendations, which fell far short of expectations, were adopted in the ­Scotland Act 2016.

That act recognised that: “The Scottish Parliament and the Scottish ­Government are a permanent part of the United Kingdom’s constitutional arrangements” and “are not to be abolished except on the basis of a decision of the people of Scotland voting in a referendum”.

It also recognised in law the so-called Sewel convention: “It is recognised that the ­Parliament of the United Kingdom will not ­normally ­legislate with regard to devolved matters without the consent of the Scottish Parliament.”

The National:

Such words are, however, useless obstacles in the path of that almighty juggernaut, the ­sovereignty of Parliament. The Scotland Act 2016 is itself just an ordinary Act of Parliament which – according to the prevailing orthodox English doctrine – could be amended or repealed by another Act of Parliament, passed in the ­normal way, by an ordinary majority.

The Scottish Parliament is permanent – ­unless Westminster decides otherwise. ­Westminster should not normally legislate on devolved ­matters – unless Westminster ­decides otherwise. In the absence of a higher, more ­fundamental, law, every right and power ­Scotland has in the Union is dependent upon the grace, favour and goodwill of a majority in the House of Commons.

Neither is this risk of violation merely ­abstract. The Internal Market Act 2020 ­displayed ­contempt for the views of the ­Scottish Parliament, being imposed by Westminster to constrain the Scottish Parliament’s sphere of legislative competence without its consent.

This is only one in a series of Brexit-related laws in which Scotland’s position was not taken seriously by the UK Government, and where Scotland’s preferences were overturned by Westminster.

READ MORE: Fresh Trident safety fears as submarines' 'life expectancy' extended repeatedly

Brexit itself was a material change to the ­conditions under which temporary consent to the continued existence of the Union was ­accepted by Scottish voters in 2014.

So, by passage of time, by immutable right, by broken promises, and by a change in material conditions, Scotland should be given another chance to vote upon its constitutional future.

However, the prevailing British nationalism of successive Tory prime ministers has stood in the way of any second referendum.

What are they so frightened of that they will not let the people decide?

Perhaps the campaign now should focus on two objectives. The first is securing recognition of the right to independence – the right to make that decision when and how we choose.

The ­second is the right to as much self-government as possible short of full independence – a ­Gibraltar or a Channel Islands solution.

The SNP should demand a commitment to those objectives from an incoming UK ­Government in return for any parliamentary support that might be needed in the event of a hung parliament or small majority.