The deal is about the political severance. Then we enter into negotiations about the trading relationships and the backstop says that, in order to preserve the open border, tariffs on either side of the border must remain the same until such time as an alternative agreement exists. If Ulster leaves the EU as part of the UK, then it follows that either Ulster stays within the EU tariff zone while Britain (ie England, Scotland and Wales) go off and do their thing or the whole of the UK remains in the tariff zone (and unable to do separate trading deals).

this makes the backstop, which is a legal requirement under international treaty into a poison pill for the Tories. They don't really care about Ulster all that much, despite their wittering on about the Union, but they do care about the votes of the DUP in Westminster.

And that's why Boris is determined to end the backstop, not the deal itself. But the backstop is the non-negotiable part which is not really in the gift of the EU to waive.

It's the ultimate Eton boys bluff. They think that speaking slowly and loudly means that they can get what they want, rules are just for little people, not bold-world conquerors like english public school Oxford graduates. Seize the day !!! They don't like it up 'em. etc etc.

This works in Westminster and to a lesser extent in Washington. It cuts no ice whatsoever in Brussels, which annoys them immensely and is part of the reason they want to leave.

keep to the Fen Causeway