So we soon discovered how sacred the notion of keeping Ireland's border open is to the EU.
The EU invoked Article 16 last night, meaning vaccines could not cross the border. And immediately made themselves hypocrites, after using the open border as leverage in UK-EU negotiations.
That they withdrew the invocation after a few hours doesn't change the fact they invoked it in the first place. It seems they intend to treat it as a tool of casual policy to manipulate the UK in any situation that is convenient to them.
They are going to find that is a form of self-harm. I doubt the Southern Irish will wear it for long. The British will fight back, of course, as we have the tools to.