Brexit, even pre-pandemic days, was always about borders. Taking back control, ending free movement, not following Brussels’ rules. Never mind that the UK always had a border with its fellow EU member states and was not in the Schengen border-free zone (itself rather frayed due to the Covid crisis).

But the UK’s internal and external borders are now getting so varied it’s hard to keep up. After two years of ultimately successful wrangling over how to keep the Irish border open post-Brexit, a new customs and regulatory border for trade from Britain to Northern Ireland beckons. Fragmenting your own market is a strange way of taking back control – but this is Brexit.

Meanwhile, Covid-19 quarantine restrictions at the UK’s borders were, belatedly, set up in early June only for the UK government to start dismantling them again within weeks. Certainly, the pandemic has been educational for many learning that health is devolved across the UK’s four nations – with police in Wales stopping English day-trippers heading across that border during lockdown. Yet Boris Johnson insisted last week that "there is no such thing as a border between England and Scotland".

Back in Brexit-land, Ireland struck a deal on Friday with its fellow EU member states on transporting its food products across the UK’s third country land bridge to continental ports without getting stuck at the back of a queue of British lorries. Ireland, after all, is still in the EU’s single market (as, partially, is Northern Ireland).

It gets worse. Once the UK leaves the EU’s single market and customs union in December, there will be new customs and regulatory checks at UK-EU borders, adding costs, hitting trade flows, impacting on travel for business and leisure between the UK and the EU.

READ MORE: Scots warned not to overdo it or face 'putting lives at risk' as beer gardens re-open 

Those borders will be a bit less hard between Britain and the Republic of Ireland since they share a common travel area. That means the new January 2021 customs border between, say, Britain and France will be the same as between Britain and Ireland, except for free movement of people. Meanwhile, the Northern Ireland-Republic of Ireland border will be open, and the new Britain-Northern Ireland border will enter into force.

Confused? It’s a messy, diverse and uncertain patchwork of borders and bureaucracy. Of course, in the face of Covid-19, people may, in some ways, become keener on harder borders. But how the politics of that works out is going to be interesting indeed.

The shimmering illusion of Johnson’s global Britain was always likely to be swept away by the realities of Brexit combined with today’s fractious geopolitics and trade wars. Covid-19 adds a whole new dynamic to that at home as much as abroad.

Brexit’s impact on the independence debate has been rather mixed. Two-thirds of Scottish voters would rather be in the EU than out on the continent’s margins. But independence in the EU, with the rest of the UK on its "global Britain" path, would mean a harder border with England and Wales.

It’s not only a choice between two unions; it’s a choice between two borders. Brexit creates a harder border with the EU; independence would remove that again while putting customs and regulatory checks on the England-Scotland border that Johnson thinks doesn’t exist.

The border question has always looked tricky for the pro-independence case. Scotland’s trade with the rest of the UK is three times that with the EU. And yes, it is contradictory for Conservatives to proclaim (wrongly) the economic benefits of borders with the EU while decrying the economic harm of borders with independence. But barriers to trade are indeed costly unless offset by other economic dynamics (arguably in the independence case by benefits of EU free movement of people, and more foreign investment).

Politically, some unionists have also played the border card to suggest with independence there would be passport checks between England and Scotland – not true if Scotland remains part of the common travel area.

READ MORE: How British nationalism is taking the place of traditional unionism 

Anyway, post Covid-19, public opinion and the politics of borders, may change. Scotland’s, so far, more effective easing of lockdown in health terms may mean some view borders more positively. Add Brexit to that, and it all looks quite messy.

For sure, the economics of an independent Scotland’s border with the rest of the UK will remain a key issue. But the political psychology of an independent Scotland’s borders, in the face of a multitude of new post-Brexit, post-pandemic borders, may be rather interesting. If it’s borders galore, some may ask does one more really matter.

All columnists are free to express their opinions. They don’t necessarily represent the view of The Herald.