Interesting! But, in this case, the problem was probably obvious when UK signed. Why has not it been properly addressed at that time?

@unamourdeswann, edited to make that clearer. It was a question of priorities. "Getting Brexit done" was more important to the Brexiteers than doing it right.

Makes sense! So to speak. Would it imply that, from the start, the idea of a "2 steps" deal was in the mind of the British part?

@unamourdeswann, speculation about the motivation of political figures is off-topic here. But it seems to be the consensus of analysts that there was no clear plan to start with, people got driven by their own rhetoric. Google "oven ready deal" ...

@unamourdeswann: "But, in this case, the problem was probably obvious when UK signed" – The problem was already obvious before the 2016 Referendum. That didn't stop Leavers to campaign and/or vote for it, though. What has only become obvious later, is that the Leavers had no plan for actually dealing with any of the problems that were already known from day 1.

@unamourdeswann the problem was well known at the time, however, a solution (that would be acceptable to all the parties) was not known at the time, is not known now, and likely is impossible. One of the important demands listed in this answer has to be sacrificed.

I don't think the Brexiteers wanted a hard border anywhere, they're mostly free marketeers. The hard border is a EU requirement as can be seen by the fact that there are no checks on goods coming from NI to GB.

@dibs487, so the Brexiteers want a free trade in goods and services? A Polish bricklayer can sell his work in the UK? Or do they insist on a free trade in a few goods and services, those which give the UK an advantage?

@o.m. well the UK is a net exporter of services to the EU and net importer of goods so yes I think they'd be very keen on free trade of services. They're not keen on the polish bricklayer as that's free movement of labour. The abolishment of which was a key driver of brexit. Ironically with the CTA there'll always be free movement of labour between uk and ROI.

I have to agree with dibs487: Claiming that the "Brexiteers insisted on a hard customs and regulatory border" makes your answer an entertaining read (due to the inherent contradiction of the bold statements), but it's completely misleading and ruins your otherwise great answer. Many Brexiteers would have been more than happy having an open border (for goods, not for people!) with the EU, without having to follow any EU regulations. (It goes without saying that this is obviously completely unacceptable for the EU, but that's not the point.)

@Heinzi, that means they want a partially open border. Letting bankers sell their services, but not hairdressers. Understandable that they want that, but a very narrow definition. "Take back control" was a key promise.

@Heinzi The sad thing is that "everyone" wants the advantages of EU, but none of the obligations (Hungary and, to a lesser extent, Poland, for example; many nationalists or populists parties in several EU countries). This completely defies the spirit that made EEC become the EU in the first place. We are falling prey to the egoism and nationalisms that the "fathers" of EU wanted to get rid of. EU has lots of problems, but divided we'll be crushed by other great powers in no time (economically). China and Russia already tried to foster divisions among EU members. Even Trump tried it.

@unamourdeswann Parliament wouldn’t have allowed a no-deal Brexit without a new referendum on that or remaining in the EU after all, and Boris Johnson was desperate to avoid that, so he signed up to a deal he hadn’t studied in detail and didn’t actually like or want because he liked the alternative even less.

@Heinzi But Brexiters absolutely did want a hard customs and regulatory border. Or are you saying they wanted to accept judgment by the CJEU as well as following EU regulations? Because not doing so means you want hard borders.

@MikeScott, do you have any evidence that Johnson did not study the detail? Well-documented, that would be worth an answer writeup.

@o.m. We have evidence (from Alan Duncan bbc.com/news/uk-politics-37439890) that Johnson never expected to win the vote. He promised anything in the expectation he wouldn't have to deliver it. He has no interest in the country, only in personal power.

@o.m. There’s been a lot in the press, e.g. independent.co.uk/voices/….

"The Brexiteers" are not a homogeneous group. As pointed out in detail on other questions, the best characterization is actually "those who are not Remainers". What the individual groups want differs radically, with the only common point that staying in the EU would make it harder or impossible, if it is possible at all. Actually, even that point is under dispute, as some think it was just a welcome rallying-point to gain relevance, power, ...

@o.m. I am not seeing as wide of a divide in remain as I am between, say, hard Brexit vs Norway model...actually the remains all seem pretty compatible with each other. Given that the original margin was very narrow... politics.stackexchange.com/a/35634/15629