Yesterday, an email appeared in my inbox to let me know that one of those Parliamentary petitions, which I’d signed ages ago and long forgotten about, has stormed past the 100,000 signatures threshold and is set for a debate in Parliament.

The subject? “Another Scottish independence referendum should not be allowed to happen”.

Now in light of recent events that sort of certainty sounds a little Spanish, just when we’ve been patting ourselves on the back for our own Government’s comparative lack of Toledo steel.

The official response is apparently the rather more lukewarm “The UK Government is clear that now is not the time for a second independence referendum.”

Policies of national indivisibility are actually normal practice for advanced Western democracies, including the United States and Germany, and under international law self-determination is not an unqualified right.

The idea that Britain should follow this norm is not new. Writing after the 2014 vote, Jack Straw suggested the following:

“Now that Scotland has decisively spoken, after a campaign whose terms were set by the SNP for itself, we should follow the example of stable federated countries (the US and India, for example) and say: “This Union is now indissoluble.”

“If independence would have been for good, so must the decision to stay. You can’t pull a living plant up by the roots again and again, and expect it to survive. Put this commitment to the Union in primary Westminster legislation. Of course, that could be changed but only by all the UK’s MPs. “Better Together” must mean what it says.”

Such a Unity Act seems unlikely to come before the House anytime soon. It is entirely contrary to the retreat-to-victory “more powers!” orthodoxy which has been unionism’s substitute for a strategy or vision since 1997. (Although as Alex Massie points out , the failures of unionism’s ‘Plan A’ are now so manifest that a rethink is clearly needed).

Nonetheless, there is still a case to be made for insisting on a substantial break, of between say 10 and 25 years, before a second referendum on Scottish independence and between any that should follow that. This is not only desirable from the point of view of those who want to keep the UK together – it’s actually almost essential for the Union to function properly at all.

To see why, let’s set aside the disputed question of Britain’s nationhood and treat the Union as the devolutionaries and federalists too often do: as a contract, rather than a country, to be maintained only as it benefits their side. Now consider what that contract entails.

Within the UK, wealth is distributed on a needs basis across the Union. Those areas which are doing well contribute more to the pot, which is then spent to support regions which need more support. Thanks to the vagaries of the Barnett Formula, Scotland does better still.

As many other writers have noted, at present majority support for the UK in Scotland hinges on this net economic benefit. But this poses an awkward question: what happens if and when the balance of fortune shifts and Scottish taxes start obviously subsidising higher public spending in other parts of the UK? In parts of England?

The obvious fear is that the Scots, lacking any deeper emotional attachment to Britain, would walk away. This provides the first, more obvious attraction for unionists of a time-lock on independence – to prevent the separatists exploiting such a window in the short to medium-term.

But the deeper case is that this “pooling and sharing” requires good faith on all sides: those who are net contributors today need to know that their countrymen stand ready to support them when the need arises. If one party retains the right to terminate the arrangement the moment they need to “pay in”, the entire system will rapidly become politically indefensible.

Without an underlying Britishness, there can in the long term be no ‘British’ money to distribute uncontroversially around a British state.

Nor is this problem confined to revenue expenditure, it applies to capital projects too. Scottish voters, having opted to remain British, naturally expect the UK to treat Scotland as a full and normal part of the country when it comes to making long-term, strategic decisions on capital projects and major infrastructure.

But this is again very difficult in an easily-broken Union. It would in fact be unreasonable and unwise for the British Government not to consider the likelihood of Scottish secession when making decisions about projects which will be paid for by, and are meant to deliver a long-term benefit to, the entire Kingdom.

These tensions, inflamed and exacerbated by those politicians whose only idea is to talk up the UK’s fragility and press onward with the dismantling of its common institutions, pose a structural and strategic threat to the Union because they undermine some of its most fundamental functions.

A moratorium thus delivers several benefits, not least by insulating the country against short-term vagaries in economic fortune (or acute stress points such as Brexit) and forcing the separatists to build a sustained and strategic case against membership.

It also provides certainty to policymakers overseeing British capital and national projects and legitimises the pooling and sharing of taxpayers’ money by guaranteeing that no party can simply walk away from their commitments the moment it suits them.

Naturally the nationalists, both separatist and federalist, will cry foul. But their grounds for objection are thin. Time-locks are perfectly normal practice in commercial contracts, and an electorate which can commit to dissolving the Union for ever can commit to maintaining it for 20 years.

One doesn’t need the steel-toed intransigence of Mariano Rajoy to see that our country has been ill-served by two decades of endlessly appeasing those who would break it up. One clear positive of the Brexit vote has been to reveal that Britain is not nearly so fragile as the “more powers!” lobby would have us believe.

Westminster must rediscover the self-confidence to defend its constitutional prerogatives and its essential role as a unifying British institution. It must also insist that, despite the cowardly and counter-productive ‘Vow’, 2014’s ‘No’ vote was no less serious a commitment than ‘Yes’ would have been.