We regret to inform you that, despite the palpable sense of relief around the country at the agreement of an 11th hour trade deal, Brexit is not done.
Sure, the disaster of no-deal has been averted.
But there are many loose ends, and even the deal itself creates the room for Brexit-related rowing with the EU for years to come.
HuffPost UK spoke to academics, think-tanks and industry figures to figure out just why Brexit isn’t done.
The biggest change we will see on day one is the end of free movement for EU citizens and the introduction of a points-based immigration system for all prospective migrants.
But the deal Johnson has signed leaves open the possibility of drawn-out arguments happening repeatedly forever if either the UK or EU wants to follow different standards.
Under the so-called “level playing field”, if either side keeps their standards in areas like workers’ rights, the environment or state aid lower than the other, they could face tariffs as punishment for unfairly competing with businesses on the either side of the border.
The deal sets up a joint UK-EU partnership council that will make sure this mechanism is properly applied and enforced.
It will have binding powers to settle disputes about unfair competition and could be the scene of Brexit arguments for years.
Another big sticking point was fishing rights, and it is far from sorted out.
The two sides agreed a five-and-a-half year transition period to allow EU boats to phase out how much fish they catch in British waters, with the UK share increasing incrementally up to an average of 25%.
And while the UK has full “control” over access to its waters after that, under the terms of the deal the EU could retaliate with tariffs if quotas for its boats end up being cut.
So the Brexit row over fish might be over for now, but there could be more to come.
July border crunch
The UK has now left the single market and customs union, meaning all sorts of rules, checks and red tape apply to trade with the EU.
But while Brussels is levying these on goods moving from the UK to the EU on day one, the government has decided to phase in import controls for goods coming here from Europe.
That means there is a whole lot that needs to happen before the so-called “full-fat border” is applied here in the UK.
This includes the construction of border control and inspection posts where full customs checks are carried out, particularly for agriculture and food goods.
IT systems, some of which were only being tested in December, will also need to be complete and operational by this point.
As recently as November, the National Audit Office expressed concerns about whether the infrastructure would be ready in time.
Ports are also expected to build extra infrastructure in time for July but the government only allocated £200m of funding to do so in mid-December.
And ministers sliced 33% off the top of every bid for cash from the port infrastructure fund, sparking warnings that the plans would have to be altered or scaled back.
One of the biggest benefits of Brexit as sold by the “leave” campaign was that the UK would be able to sign new trade deals with countries around the world like the United States and India.
But up until now, the UK has simply signed so-called rollover deals with the likes of Canada, Japan and Mexico, so it can continue enjoying the trade terms it had with these countries through their existing deals with the EU.
Rollover deals are yet to be signed with Albania, Algeria, Bosnia and Herzegovina, Cameroon, Ghana, Montenegro, and Serbia.
That’s before we even get on to the big prizes of deals with the likes of the US, Australia and New Zealand.
The ultimate goal of a big agreement with America also looks a more distant prospect since Joe Biden’s election victory over Donald Trump.
Biden has been much more lukewarm about the UK’s decision to leave the EU than Trump and has publicly warned about the impact it could have on peace in the island of Ireland, and a trade deal is unlikely to be an early priority for the president-elect.
With free movement coming to an end, more than three million EU citizens in the UK have been asked to apply for “settled status” to ensure their rights can continue after the end of the transition period.
There is also a further grace period of six months to June 30 for EU nationals to secure their rights in the country.
But the government will have to deal with a big question about what happens to those EU citizens who have not been able to get the relevant documents, despite being eligible to do so.
They could in effect become undocumented, losing the right to employment, housing assistance, benefits and access to the NHS.
Ministers will have to decide whether they can continue working and living in the UK, and will be keen to avoid another Windrush-like scandal.
Meanwhile, the UK will need to figure out how to plug gaps in the workforce, with the Migration Advisory Committee warning that the end of free movement could lead to “stark” shortages of workers in areas like social care.
Northern Ireland’s status after the end of the Brexit transition period was meant to be sorted out in the withdrawal agreement (WA) that Johnson signed to take the UK out of the EU on January 31, 2020.
But then the UK decided it wanted to break international law in a “limited and specific way” by giving ministers the power to go back on the WA. A row ensued and a deal was struck between Michael Gove and Brussels to finally sort the issue.
Unfortunately, Gove’s agreement also contained a number of temporary measures that will need revisiting in the near future.
It’s all because Northern Ireland is operating in a kind of halfway house, following many EU rules on trade so it can keep an invisible border with the Republic.
Gove’s deal includes a temporary agreement to class goods currently in circulation in Northern Ireland on January 1 as “qualifying”, allowing them “unfettered access” to the UK mainland.
But in the second half of 2021 there will need to be new measures to ensure traders with that “qualifying status” can check in at ports and airports to exempt them from controls and tariffs on goods moving from Northern Ireland to the UK mainland. Full controls will apply to “non-qualifying goods”.
To get around the EU’s ban on importing unfrozen meat, Gove’s deal also secured a grace period until April 1 to allow supermarkets and “trusted” suppliers to move products like chilled meat and sausages to Northern Ireland from the UK mainland for six months.
Long-term, both sides have agreed to find a way forward to minimise controls in this area.
But unless they strike a new deal, EU rules will apply and the supply of sausages to Northern Ireland is in doubt.