Analysis by Luke McGee, CNN

(CNN) -- With all that's happened in 2020, you could be forgiven for forgetting that back in January, the United Kingdom left the European Union.

Ever since, the UK has been in something called a transition period, designed to prevent the economic and logistic chaos that would result from a hard crash out of the world's largest trading bloc and all the legal and institutions that bind together the EU's member states.

Predictions of what that disruption might look like include shortages of food and medical supplies into the UK and a sharp reduction in exports from it, as the rest of Europe deems it too much hassle to trade with a country outside of its common legal infrastructures.

Well, that no-deal crash out is a real risk once more, as the transition period is set to expire on December 31. The two sides had hoped to negotiate a post-Brexit agreement in trade and other potential areas in the 10 months since Brexit happened. However, the eagle-eyed among will note that we are in the first week of December and a deal has yet to be agreed.

Theories vary as to exactly how close a deal is dependent on who you talk to.

The EU would argue that the UK moved its goalposts soon after negotiations began. Instead of negotiating explicitly for a trade deal that would ensure "no tariffs, fees, charges or quantitative restrictions across all sectors with appropriate and modern accompanying rules of origin," chief negotiator David Frost informed Brussels that the UK wanted something far less comprehensive.

The UK would argue that the reason its position changed is that the EU stopped negotiating in "good faith" when it opened with demands on a level playing field which would curb the UK's ability to diverge from the EU's rules and regulations, especially on state aid. Other areas of contention have been Brussels' demands for access to British fishing waters and some kind of European legal oversight of any deal. The UK has for months said that these do not respect the UK's sovereignty and are therefore unacceptable. That, in a nutshell, has been the state of play for months.

The talks have not been helped by the pandemic. Negotiations were held virtually, something which officials on both sides have told CNN made progress difficult. Elements of Britain's domestic politics also created tension -- the government introduced legislation over the summer which would breach the treaty it signed with Brussels last year. This even caught the attention of President-elect Joe Biden, who indicated that he would not countenance a formal trade deal with the UK if it pressed ahead with this policy.

However, things finally seem to be moving. EU officials believe that talks are entering their final hours. The looming reality of a no-deal crash out at the end of the year has, Brussels sources believe, sharpened minds on both sides. An official working directly for the EU's chief negotiator, Michel Barnier, told CNN that talks "do need to get wrapped up now. It's now or never."

Diplomats working for member states are equally convinced that the end is near, with one saying that a "sword of Damocles" is now hanging over Boris Johnson's head. However, others in Brussels who have direct knowledge of the negotiations are still cautioning for prudence and believe that setting any such hard deadlines is unwise. "Substance remains more important than a timetable," another diplomat told CNN.

Fears that no deal might be reached still remain, with officials and diplomats from all corners of Brussels worried that Barnier's negotiating mandate is running out and that there isn't time for the 27 EU member states to grant him the freedom to make concessions that would break the deadlock.

Whichever way you look it, time is not on the side of those who sincerely want a deal. One way or another, it's likely we will know the outcome. And should the talks collapse, the UK will be left with weeks to prepare for the largest shock to its economy for decades.