Published: 5:54 PM August 24, 2019 Updated: 8:43 AM September 18, 2020

JAMES BALL looks at the revelations from the Operation Yellowhammer leaks, and it confirms a no-deal Brexit would be absolute chaos.

The Yellowhammer is a songbird found in the UK and right across Eurasia, named for the distinctive bright yellow feathers on its head. It has been the subject of poems by Robbie Burns and John Clare. In the UK, its population is in severe decline and the bird is red-listed as a conservation risk - but across Europe and the world, the bird is doing well, and is recorded as a species of "least concern" from a conservation perspective.

Given this backdrop - a UK population in crisis against the rest of Europe facing more gentle decline - it's hard not to suspect someone in the UK government or civil service was trying to send a signal with the name of the UK's contingency planning for a no-deal Brexit: Operation Yellowhammer.

Details of the UK's scenario planning - working out the potential effects of a no-deal Brexit, given the current status of UK and EU preparations for it - were splashed across the Sunday Times, setting out the potential for shortages of food and medicine, disrupted fuel supplies, potential for civil unrest, and turmoil at ports.

The numbers are startling. The government expects that 50% to 85% of HGVs to be unready for French customs on day one, and as a result expect Channel freight to plummet to just 40% to 60% of its usual levels. This won't be short-term disruption - even after a further three months, they only expect trade flow via our busiest and most crucial trade route to hit 50% to 70% of its usual level.

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The consequences of this are severe. Around 75% of all medicine entering the UK does so via these "short strait" routes, and there are serious limits to how much could be stockpiled in the short time before a potential no-deal - just ten weeks - plus limitations based on the shelf lives of many medicines.

The time of year we are heading in to no-deal could hardly be worse. Unlike in March, the end of October marks the end of the UK growing season and the beginning of our peak reliance on imported fresh food. The government doesn't anticipate overall food shortages - hurrah, we won't actually starve - but shortages at the supermarkets, especially of fresh food, seem inevitable.

This is all compounded by internal risk assessments obtained from councils by the BBC, showing the preparations needed by organisations at the front end of the impacts of no-deal. This could include needing to drop nutritional requirements for school lunches, care homes needing to stockpile food, and preparations for civil unrest, even in situations far from the worst case.

In short, every credible assessment from the public authorities responsible for mitigating no-deal say it is still going to be absolute chaos.

But perhaps more interesting than the leaked material itself - which contained few warnings anyone paying attention to Brexit wouldn't have heard before - was the chaotic and contradictory response by first the government and then its outriders to the publication of its own plan.

Michael Gove, the cabinet minister in charge of preparing for no-deal, tweeted that the plans were old and dealt with the absolute worst-case scenario, without any kind of mitigation or work done to manage the impacts of no-deal, even as others pointed the fingers to disgruntled former ministers (left unnamed) who must have leaked it.

A key part of the implication of that response was this was outdated information from a previous administration that did not really believe in Brexit, and so could safely be dismissed as Project Fear.

The problem with this response is that neither element of it is true. The Operation Yellowhammer report is published monthly, and circulated around key officials who need it, including those in devolved administrations. Multiple reporters quickly managed to confirm that this report did, in fact, date from August - and so from Boris Johnson's premiership.

Furthermore, this is nothing like the worst-case scenario, and instead contains the likely situation of no-deal given not only what the UK government has done to manage its impacts, but also what EU countries have already done.

This is the reason it doesn't include things like grounded flights and so on - the EU unilaterally took steps to prevent this happening in the event of a no-deal, if only for a few months. This also takes into account measures the French have taken - entirely of their own accord - to manage the disruption at their ports which no-deal would cause, while still complying with EU requirements.

The leak was not the worst-case scenario - it is the most likely outcome, as the UK government sees it. There could be much more that they don't see, especially if the crisis planning fails.

We are now in the absolutely bizarre and dangerous situation where we are 10 weeks away from a once-in-a-generational crisis and the government is denying its own preparations for that event.

To heighten the strangeness, the government is planning to spend £100 million in a public awareness campaign on how to prepare for no-deal, even as it conceals and denies the very real planning going on behind the scenes.

On what does the government plan to spend £100 million? On the false reassurances that everything is fine that its ministers spout, or on the real action businesses and individuals must take to avert total meltdown? The UK government is about to spend one of the biggest public advertising budgets in history at a time when no-one can trust its messaging.

This could prove the most dangerous unknown element of no-deal: every contingency measure relies on avoiding panicking, protesting, and rioting. If the public start large-scale panic buying, we will have serious food shortages, and cascade effects. We need trustworthy, detailed information on planning. We need reassurance. We need to feel like the government has a grip on what it's doing.

Surely few people indeed have that reassurance right now. Perhaps Yellowhammer is an apt name for our no-deal planning - but the birds, at least, can fly away to Europe this autumn.