The United Kingdom's days are done.

I'd rather we admitted that calmly and built something better, than discovered it in the wreckage of an acrimonious break-up.

Look at the last 72 hours.

Saturday, Dublin. Donald Trump, beside the Taoiseach: "I'd love to see it unified." Then, subtlety not being his style, "It's going to happen eventually. It may as well happen now." By Sunday, Irish unity was "one of the naturals of all time", and he wouldn't discuss Scotland "yet".

Monday, Cardiff. Swinney, Rhun ap Iorwerth and Michelle O'Neill sign a memorandum declaring that "Westminster's time is coming to an end" and that "no Westminster government has the right to block democracy". Swinney calls Andy Burnham "the last prime minister of the United Kingdom". Mary Lou McDonald says Micheál Martin "needs to catch up".

Within hours the DUP's Emma Little-Pengelly is disputing whether O'Neill had any authority to be in the room at all, accusing her of trying to "weaponise" the role.

And Downing Street? Burnham told the Commons a Scottish vote could happen given "clear consensus", then wrote to Swinney saying it remains "off limits".

That's the acrimony. On day one.

Two clarifications before anyone gets carried away.

Devolution is not independence. Swinney's argument is that Burnham believes decisions belong close to people, so must concede referenda. That's a leap, not a logic. Subsidiarity is about where power sits inside a state, not a case for leaving one.

And there is no majority. Scottish independence has sat around fifty fifty for years. Irish unity polls well short in the north. The mandate being claimed this week doesn't yet exist.

But it will, if nobody fixes what's generating it.

Because nobody designed this. Devolution was handed out piecemeal and can be withdrawn by statute tomorrow. The funding formula was a 1978 stopgap that allocates by population and has never once asked what anyone needs. The investment rulebook sends capital to places for the crime of already being rich, then calls it value for money. And a land border runs through one island run by two states, so the frontier gets moved to the Irish Sea and two million people live under rules made in a room they don't sit in.

None of that is any government's fault. It's what you get when one nation holds eighty four per cent of the population, there's no written constitution, and Westminster is at once the English parliament, the Union parliament and the referee between them.

Changing the government changes nothing. The output is a property of the structure.

So change the structure, deliberately, while there's goodwill left to do it with.

Goodbye United Kingdom. Hello Union of the Isles.

England, Scotland, Wales and Ireland, the whole island, entering as four founding equals. The UK dissolves on day one, because nobody is joining anybody else's country.

Tomorrow, how it works, and why every objection you're forming already has an answer.

Hold your postcards until then.