Assuming that HMG sticks with its apparent plan of scrapping parts of Withdrawal Agreement and doing without an EU-UK trade accord, I foresee 10 consequences - a short thread. @CER_EU /1

The PM wants to eliminate the border in Irish Sea. That means a border of some sort between NI & ROI, to police EU's single mkt & customs union. In the view of many, including most ROI politicians, that endangers Good Friday Agreement. One reason Republican terrorists..../2

laid down their arms was that that border went. So consequence 1) A very bad UK-Ireland relationship. Consequence 2) An annoyed US political class that will block any UK-US trade accord (as Pelosi has spelled out). Consequence 3) Increased likelihood of violence in NI... /3

though there is of course never any justification for violence. The EU was united in its support for Ireland in Brexit talks and in its backing for Withdrawal Agreement. So UK will have embittered its biggest trading partner. /4

Consequence 4) This acrimonious Brexit will make future UK-EU co-op on defence, foreign policy and security much harder to achieve. Such co-op requires trust, confidence & goodwill, which the UK move to breach international law has damaged. A weakened Europe will delight some. /5

UK leaving without a deal may not be a permanent state, but it will be long enough to hurt. Consequence 5) chaos at GB's borders (even WITH a deal some of that would happen, eg IT systems not ready). EU could lack motivation to minimise friction through customs cooperation. /6

Consequence 6) 'WTO rules' means high tariffs that would hurt sectors of UK economy such as car-making and livestock. Consequence 7) UK has been counting on EU granting it data 'adequacy', which is a decision for the EU; ditto for 'equivalence' for financial services. But../7

Both require the EU's goodwill, which may be lacking, with serious consequences for important sectors of UK economy. The long-term impact on Britain's voice in the world is unclear. But consequence 8) UK won't be able to tell other states to respect int'l law, eg on Hong Kong../8

without provoking laughter. And then there's the impact on UK politics. HMG's reputation for competence is already an issue, post-COVID-19 & school exams. Consequence 9) A chaotic Brexit will persuade more voters that the govt is incompetent. Labour is bound to benefit. /9

Consequence 10) Scottish independence moves closer. For many Scots, leaving the EU is bad enough. Leaving with an extreme model of Brexit that harms the economy is worse. If support for SNP surges in May's Scottish election, it becomes harder for London to resist #indyref2. /10

It is hard to imagine that the UK can remain without an FTA with its main trading partner for long. But EU will insist on a withdrawal agreement that delivers no hard border on island of Ireland. That means UK accepting either May's deal..../11

(UK de facto in EU customs union & single mkt for goods), or Johnson's deal of October with a border in Irish Sea. I am confident the EU would not betray the Irish on the border. This means that any UK govt that wants a trade deal will have to give in to the EU on Ireland. /ENDS