The motto was supposed to be 'we are all in this together' - not 'the places someone picks out on a map are but the rest of you are not'. In a pandemic you ought to prioritise national unity not disunity.
They really should have created a war cabinet from day one and decided these things on the basis that viruses will never know they have crossed a border - be it from GM to Cheshire or England to Scotland or Wales.
Very possibly N Ireland and Ireland should have done the same on that island too.
I suspect the rest of the world think prioritising political disunity over a plan for these small islands as one was a very silly error.
It's an interesting point, and I largely agree with you, but I have a German friend through football, who lives close to the border with Holland, and not that far from Belgium, and obviously there are no "borders" in reality.
About 6 -8 weeks ago, the cases in his state in Germany where low, but high in both Belgium and Holland, and cross border shopping is the normal, in fact people even nip across the border for things petrol/diesel even, due to different taxes.
Both countries locked down about the same time, and subsequently their cases fell, but as we know Germany cases have risen, so there is probably a risk of reinfection back into those countries now, so where do you draw the line ?
Germany has a very long land border over 2000 miles, and with 9 different countries, it also has 16 different internal Federal States, all to a degree governed independently, 3 of the states are "City States" within larger states. They've had different rules in place throughout just like we have, I don't know if they have a universal system which would be unlike us, but it's very complicated for large countries with states within, so we are no alone, and europe has "open borders". I don't know if other countries have tried to prevent travel across borders, but I'm pretty sure Germany hasn't, in fact some people will cross the border for work in some areas.