When David Cameron in 2012 agreed to an independence referendum in Scotland, it was seen as a wise move for a unionist.
Support for remaining in the UK at the start of the campaign was so high – about 70% of Scots – that the plebiscite looked set to settle the matter.
By election day in autumn 2014, when staying in the UK won by only a 55:45 margin, Cameron was depicted as having been reckless and arrogant for calling a needless referendum and so opening a separatist can of worms.
In fact, as we now see with events in Catalonia, the original analysis was correct – Cameron did the right thing in letting the Scots have a vote.
That country might yet leave the UK but it is far from guaranteed, partly because there is not the widespread rage in Scotland that there would have been if they felt a Tory British prime minister had denied them the right to determine their own future.
In Catalonia, however, there is now that rage. And this makes me think the region will leave Spain.
The process by which that might actually happen is hard to foresee. Spain has constitutional protections against secession that are not present in the United Kingdom.
But there could now be prolonged disorder and civil disobedience in Catalonia, giving momentum to the separatists (who in recent years seemed to have only large minority support, as in Scotland in 2012).
It was foolish for Madrid to allow police to be heavy handed. But the federal government was in a bind. If Spain had just let what it said was an illegal election happen, and the Catalans had claimed victory and declared independence, there would have been chaos in any event.
I was in Catalonia in 2014, weeks after Scotland and just before its own independence vote (also deemed illegal by Madrid, until downgraded by the Catalans as a chance for voters to express their views).
I wrote a story asking locals if they had been following events in Scotland, and overwhelmingly they had been. They were impressed London had allowed a vote. Madrid’s refusal to do the same seemed to be fuelling nationalism. And that was before yesterday’s scenes.
If Catalonia does go it will rock Europe to the core, and bolster separatists everywhere. Scotland will be more likely to split from the UK than if Catalonia stays.
And make no mistake – if both Catalonia and Scotland go, it will reinvigorate nationalist feeling here, and bring closer a border poll.
All eyes will then be on how the centre ground – the young Alliance and Green voters, who were very anti Brexit – divide. This is why Sinn Fein – never slow to miss a trick – has been in Catalonia in recent days.
Unionists can take comfort from the fact that support for Irish unity seems not to have risen much in the year since the referendum decision to leave the European Union.
• Ben Lowry (@BenLowry2) is News Letter deputy editor