It’s 11:00pm GMT – midnight on the continent – on Friday 29 March 2019. The United Kingdom is now officially outside the European Union and Prime Minister Boris Johnson makes a live address to the nation: “I am not frightened by what lies ahead and I don’t believe the people of Great Britain are frightened by what lies ahead,” he tells viewers, plagiarising Ronald Reagan.

President Trump has been appearing on news bulletins during the day wishing his “good friend Boris all the best” during what he grinningly anticipates will be a “kinda tough period, but it'll all be fine. Just fine.”

After a Daily Express campaign, Johnson has extended pub closing times by one hour, but no one is in a mood to celebrate, certainly not in the City. The consensus in the Square Mile had been – even until the final days – that the government would agree to a realistic deal with the EU. Theresa May's abrupt resignation – one week before Brexit, as she announced she couldn't go through with something that would damage her country so profoundly – shook confidence at home and abroad.

Sterling subsequently begun to slide sharply and, by Brexit Day (or Independence Day as Trump still calls it), the pound was down to $1.10 against the dollar – a fall of more than a quarter from $1.50 just before the 2016 Brexit vote. Nigel Farage has once again been photographed beside a computer screen smiling broadly as the slide continued. While UK multinationals with large operations overseas have benefited, the more domestically focused UK stocks see their prices decimated.

Flights between UK and EU destinations cease shortly after the witching hour on the 29th because commercial pilot licensing is no longer mutually recognised by the UK and EU. As the weekend begins, tens of thousands of tourists and business travellers find themselves stranded on both sides of the channel, at airports and sea ports alike.

The start of British Summer Time on the 31st only worsens the rapidly escalating logistical chaos. At the approach roads to the Eurotunnel terminals and sea ports there is gridlock as commercial goods lorries and holidaymakers' cars sit backed up in queues that are already stretching for dozens of miles.

The modest numbers of additional customs officers so far recruited by the UK, France and the Netherlands are proving themselves ill-prepared and completely outnumbered as they desperately try to manage the vast queues growing hourly at the UK border.

Within days, stocks of some specialist foodstuffs imported from the EU are dwindling. Within a few weeks, supermarket shelves beyond the home counties have started to empty.

More critically still, vital supplies of pharmaceuticals are beginning to disappear from dispensing pharmacies, even though many hospitals had started stockpiling drugs months ago, putting patient care and lives at risk.

Shops are closing, container ports are grinding to a halt, car production slows and eventually ceases.

As public disquiet grows, Johnson – not for the first time – disappears from public view and the Armed Forces are called in to help to manage the border, guard against civil unrest and support the delivery of critical public services.

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All of these scenarios for a post-Brexit Britain are real possibilities. Even that last and possibly most alarming prediction in a long list is not mine alone: recourse to the Army was what Philip Rutnam, the permanent secretary at the Home Office, blurted out when he was asked how Brexit would all play out by the home affairs select committee last year.

I really do wish all of this could just be dismissed as Project Fear, but, honestly, when the government has no strategy in place for leaving the European Union, and when I ask repeatedly what happens on 30 March 2019 if it’s a “no deal” which means “no transition” the silence is terrifyingly deafening.

The fact is few in government have thought through what life for ordinary citizens will actually be like on 30 March 2019. I don’t discount the possibility that whoever is leading our country by November 2018 – and we can only hope it won't be Johnson – may be able to come up with a deal that can credibly be ratified by the EU. That would be no mean feat, but it would mean that Brexit Day would, in theory, be relatively straightforward. For the 16 million Britons who voted Remain, it would, of course, be a sad day; but there would, at least, be an agreed settlement between the UK and EU, agreed transitional arrangements and a clear understanding of how future structures and processes would work.

A no deal Brexit looks, however, increasingly likely. It even appears to the preferred outcome of some Brextremists whose cult-like obsession appears to be leaving the EU at any cost, as Anna Soubry conceded yesterday, something a great many of us had under-estimated.

The situation is grave, but not hopeless. Let us take comfort in one unarguable but all too rarely acknowledged fact. In spite of the triggering of Article 50 by the government, the endless debates in both Houses of Parliament and the clod-hopping negotiations with the EU27, we have not yet left the European Union.

Nor will we, until the clock strikes 11:00pm GMT on Friday 29 March 2019. Until that hour, anything can happen. We could still choose to revisit the decision we took in June 2016. The countdown could even be stopped if both the UK and EU were to decide that this was a sensible stop-gap for a nation that had got itself into a bit of a fix: that’s a possibility that grows as each day passes by without significant progress being achieved in the negotiations between Michel Barnier and, now that David Davis has fled, Dominic Raab.

Still, if no agreement has been secured by November, then the risk of a no deal scenario rapidly, and bleakly, accelerates.

Brextremists will of course accuse me, as they always do, of doom-mongering, but rarely in peacetime have the threats to our country been so grave, so easily quantifiable and – perhaps most tragically of all – so avoidable.

Is the government in control of events? Who can honestly say? What I do know is that a shadowy, cross-government outfit called the Border Planning Group – set up by unidentified permanent secretaries – is now apparently weighing up the implications of this potential catastrophe, and is, allegedly, trying to work out how to manage the aftermath.

Strangely enough, few in Whitehall or Westminster know anything about this group, neither what it’s doing or what assessments it’s arriving at. This is, I suggest, no time for smoke and mirrors. No time for soundbites and people like Johnson airily telling apprehensive colleagues “it'll all be fine.”

The time has come for ministers to come clean about the assessments they have made about the implications for all of us, and our way of life, in the event of no deal. This is the responsible, transparent and decent thing to do. We need to know now what Brexit really means.