This is the crux of it. The issue that was kicked down the road for 4 years has reached a dead end. Brexit hardliners want access to EU market but won’t accept level playing field because ‘sovereignty’ or a barely concealed desire to deregulate. https://www.businessgreen.com/news-analysis/4024619/nursed-ratchet-brexit-talks-end-began-stand-sovereignty-standards BG+

And it is not in any way in the EU’s interest to concede to such demands. Why should it accept on trust that UK won’t undercut its businesses on pollution standards, for example, when assurances are coming from a government that just tore up its own manifesto to cut overseas aid?

The EU has moved considerably on this. The original plan was for binding regulatory alliance and non regression clauses. The EU is now recognising UK sovereignty and saying UK can diverge if it wants, but to do so would mean pollution tariffs and the like.

What the UK and the Brexit hardliners have never really explained is what is so unreasonable about the EU wanting to defend the integrity of its market?

Got to fear cakeism is about to be tested to destruction.