What a paradoxical story we shall tell our grandchildren about Brexit. The little ones will climb on our knee and we will recall how we bravely seized our independence from hated Brussels – only to destroy our country. Their infant brows will furrow in confusion when we tell them that in order to make Britain great again, we smashed it to pieces.

Was this some kind of terrible accident, they will ask. And we will have to say no, this was deliberate. Our leaders thought escaping the European Union was so vital it was worth shattering the deeper, closer union that had defined our country for more than three centuries. So great was their professed patriotism that they had to break the thing they loved.

But let’s not get ahead of ourselves. Let’s begin instead with the Brexit-related event that would once have been the biggest news story of the month but which was, such is the current, fevered state of things, almost forgotten in the stampede. The government U-turned on the signature proposal of its budget the previous week: the demand that the self-employed pay more in national insurance contributions (NICs).

The connections to Brexit are clear enough. For much of the leave-supporting press, Philip Hammond’s climbdown was alarming because it sent a signal of weakness to the remaining 27 EU states with whom Britain will soon be negotiating a divorce. On this view, Europe’s capitals were bound to have watched the U-turn and concluded that they could push Theresa May hard: under the slightest pressure, she is sure to cave.

In fact, the implications are the opposite, but no less troubling. Hammond’s humiliation suggests May will never, ever allow herself to be on the wrong side of the Daily Mail, which disapproved of the NICs move: far from being a pushover at the hands of the EU 27, she won’t be able to make even the slightest concession. If she budges on, say, the exit fee, the Mail will tut and she’ll buckle. This augurs badly for the possibility of any viable deal.

Just as alarming are the signs that backbench Tory rebels – centred on Michael Gove and Iain Duncan Smith – had it in for Hammond not because they care deeply about the self-employed, but because they wanted to wound a chancellor who, like May, voted remain, and whom they saw as the strongest obstacle to a hard Brexit. Hammond is now duly weakened and there is no one around the cabinet table strong enough to stand in their way.

That matters, given that the Brexiteers seem engaged in a competition to advance ever more macho versions of EU divorce. The way things are going it will not be long before, in Tory circles, merely leaving the single market and customs union will be deemed insufficient: Brexit for wimps. Only crashing out of the EU, forcing Britain to trade on masochistic WTO terms, will be seen as sufficiently hardcore Eurosceptic. Advocating a deal with the EU, and being willing to compromise to get it, will be cast as the new Europhilia.

In normal times, all this would be disturbing enough. But it was dwarfed by the greater act of self-harm: May’s response to, and responsibility for, the SNP’s call for a second independence referendum in Scotland.

That demand is predicated on the argument that the Westminster government has failed to consult with the devolved nations to forge a truly UK-wide position on Brexit. You might say that no amount of consultation would ever have been enough for Nicola Sturgeon, that whatever May had offered wouldn’t have been enough. But simple politics demanded that May at least try.

Had the PM made a big show of involving Edinburgh, Cardiff and Belfast, Sturgeon’s case would have been weaker. As it is, May has indeed looked as if she is pursuing a Brexit designed solely to placate the Euro-loathing wing of the Tory party, rather than satisfy the complex needs of the whole UK. That the country voted only narrowly for Brexit and that two of these islands’ four nations – Scotland and Northern Ireland – rejected it outright, May seems to have forgotten.

It will not be long before merely leaving the single market and customs union will be deemed insufficient

By that simple failure, May has allowed a situation to arise which imperils the integrity of the United Kingdom. Whatever the legal position, political reality says she cannot deny an elected Scottish parliament a referendum if that’s what it wants. The only argument is over the timing. When, not whether.

Given everything that’s happened, only the bravest punter would bet that Scotland won’t seize this second chance and vote to go it alone. Brexit has surely boosted the independence case. How can a Brexit government argue against independence now, without sounding like screaming hypocrites? If May warns that it’s risky to break away from a union with your closest neighbours and trading partners, taking a leap into the economic dark and putting up needless borders, Scottish voters would laugh in her face – and have every right to do so.

A finger-wagging Tory prime minister in London, a Labour party whose weakness apparently guarantees Tory rule for another decade if not longer, and the fact that Scotland did not choose the Brexit path – all these should make the ground fertile for a renewed yes campaign.

There is a counter-case, and it will be made this weekend by the man whose intervention was so crucial in 2014’s Scottish independence referendum: Gordon Brown. In a speech in his hometown of Kirkcaldy, the former PM will argue that, done the right way, Brexit could make the argument for the union stronger now than it was three years ago.

Back then, the yes campaign promised a future in which an independent Scotland within the EU could still trade friction-free with the rest of the UK, because both would be in the European single market. Now, even if Scotland keeps its place in the single market, the UK it leaves behind would be outside it. The home nations of these islands would be on opposite sides of a trade wall.

Brown invokes a “third option” between Brexit conservatism and SNP nationalism. This option would see powers currently exercised by Brussels handed not to London but Edinburgh. Suddenly Holyrood could set its own sales tax, unbound by EU rules on VAT, and back key industries such as shipbuilding, freed of the old EU rules barring state aid. Brown envisages a Scottish parliament muscular enough to sign its own international agreements and get a grip on fisheries and farming, areas where the big decisions used to be taken in Brussels. By staying in the UK, Scotland would have not just all these new powers but the resources – the cash – to make them real, resources it would lack on its own.

It’s a strong case, with Brown doing what he does best: reframing a debate on terms that suit his side and wrongfooting his opponents. If the clash is presented as a choice of Scotland versus Tory Westminster then of course independence will win. But if people see his “third option” as the best of both worlds, then maybe the union can just about hold.

The worry though is that, as 23 June 2016 showed, referendums are not always only about voters choosing the best policy prescription. They are also about emotion and mood. Who knows how Scottish voters will approach a plebiscite in, say, 2019? None of us do, and that includes Theresa May. And yet she is prepared to risk it. Such is the madness of Brexit: wilfully endangering the survival of our own country – and calling it liberation.