Britain formally left the European Union at the end of January, just before the pandemic struck. If you think you might have missed the consequences of that historic exit because of coronavirus, you'd be wrong.
Our neighbour remains a de facto member of the EU's trading arrangements until the end of this year. That 'transition period' has allowed Irish businesses to buy stuff from British businesses exactly as they have done for decades, and vice versa.
But Brexit in name only will not last much longer. 'Frictionless' trade across the Irish Sea will end on the first day of 2021. That much has been clear since Boris Johnson's government ruled out extending the agreed 11-month transition period. More time would have allowed each side's negotiators more scope to cut a detailed and comprehensive long-term deal (trade deals between modern economies are inevitably complex).
Less clear is how much friction there will be for businesses trading across the Irish Sea from the beginning of next year. That is because the EU and the UK are still slugging it out on the terms of their future relationship.
What's at stake and what's the problem?
First, some perspective. The economic calamity caused by the pandemic is far worse than the worst 'no deal' Brexit. But that says more about the gargantuan shock the world is currently experiencing as a result of coronavirus than it does about how bad Brexit could be.
Many, if not most, businesses have been negatively affected by the pandemic in one way or another. The negative impact of Brexit for businesses selling into the British market has been much discussed in recent years.
Suffice to say that to erect new barriers to trade across the Irish Sea in the middle of the Covid crash would be a disaster for many companies, and could push many of them over the edge.
If the plight of exporters is well known and much discussed, the risks of possible shortages of essential supplies in January need more attention.
Ireland remains highly dependent on Britain as a source of imports - from the flour that goes into bread to the petrol that goes into our vehicles. In the first half of this year, one in four euro spent by Ireland Inc on foreign goods went to UK businesses, making Britain our single most important source of goods.
But even this does not illustrate how significant any disruption to Irish Sea supply lines could be for Ireland. Two other factors are relevant.
First, it has often been said that Ireland exports everything it produces and imports everything it consumes. This is not quite true, but it is much truer than for bigger economies, such as Britain, which produces a wider range of goods. On a per-person basis, we in Ireland import around four times more goods than the average Briton.
The other additional reason a messy Brexit would amount to a second supply whammy, to add to the one inflicted by the virus, is the role our neighbouring island plays as a land bridge to and from the Continent. Most of the nuts, bolts, food products and everything else consumers and businesses buy in from the rest of the world comes from continental countries. Much of the merchandise coming to Ireland on trucks comes through Britain because that route is much faster than sailing directly from the Continent.
Having well-stocked shelves in supermarkets and factories across the country depends on goods coming from or through Britain. Any significant disruption at that country's ports and/or Irish ports poses a real threat to what is an economic artery. Because every man, woman and child in the country consumes imported goods, including basics such as food, it is vital that supply lines work efficiently and that ports do not back up, which is exactly what could happen if there is no EU-UK trade deal. It could also happen even if there is a deal, and that deal includes lots of new checks and import taxes.
With less than four months until the transition period ends, yesterday Michel Barnier, the man leading the EU's team in the Brexit talks, spoke at the Institute for International and European Affairs (where I work).
While acknowledging repeatedly the 'particular' problems and risks Brexit poses to Ireland, he made it plain that he was not happy with the way the talks were going. The Frenchman sounded downbeat on the prospects of a deal. He said that any deal will have to be struck by Halloween in order to give the lawyers time to write it up and the legislators across the continent time to give it the thumbs up in their respective parliaments.
Barnier highlighted three big blockages to a deal. One is how to divvy up fishing rights in the waters around these islands. Another is what sort of refereeing system should exist if either the EU or the UK believes the other side is breaching whatever overall deal is agreed.
Both these issues are narrow enough in content to allow agreement to be reached quickly, provided the political sensitivities on both sides can be overcome.
The third issue blocking a deal is cash from Her Majesty's coffers being used to subsidise businesses in Britain. This is the most important issue economically, and also the trickiest to find a workable solution to.
The British say the reason they are leaving the EU pitch is so that they are no longer bound by rules of this kind. The EU see companies in Britain being able to out-compete theirs thanks to handouts from Whitehall - and we in Ireland have particular concerns that foreign companies here could get lured across the water with promises of multi-billion pound grants and incentives.
If there is no deal in the weeks ahead, we will spend what is likely to be the least merry Christmas in decades fretting about shortages of a range of goods from the moment the new year is rung in. Everyone needs to refocus on this risk in the weeks ahead.