Under pressure, the British Government has finally published the 20 “reasonable worst case planning assumptions’’ under codename Operation Yellowhammer. Here are the key points.

First published in September 2019.

Boris Johnson and his government were under pressure to release the document, especially after it was leaked to the Sunday Times last August, and after the appalling treatement of Dr David Nicholl by Jacob Rees-Mogg in the House of Commons, last week.

Here are the Key Points of what would happen on Day 1 of the UK leaving the European Union with no deal, as stated in the document:


● The UK reverts fully to ‘third country’ status.

● France will impose EU mandatory controls on UK goods.

Between 50-85% of Heavy Goods Vehicles (HGVs) travelling via the short Channel Straits may not be ready for French customs.

● The worst disruption to the short Channel Straits might last for up to 3 months.

● In a reasonable worst case scenario, HGVs could face maximum delays of 1.5-2.5 days before being able-to cross the border.


● The Border Delivery Group and Department for Transport forecast significant disruption lasting up to six months, which will have an impact on the supply of medicines and medical supplies.

● On the reliance of medicines and medical products’ supply chains on short straits crossing: Whilst some products can be stockpiled, others cannot due to short shelf lives - it will also not be practical to stockpile products to cover expected delays of up to six months.

● Any disruption to reduce, delay or stop supply of medicines for UK veterinary use would reduce our ability to prevent and control disease outbreaks, with potential detrimental impacts for animal health and welfare, the environment, and wider food safety/availability and zoonotic diseases which can directly impact human health.

● Industry stockpiling will not be able to match the 4-12 weeks’ worth of stockpiling which took place in March 2019.

● An increase in inflation would significantly impact adult social care providers due to increasing staff and supply costs, and may lead to provider failure, with smaller providers impacted within 2-3 months and larger providers 4-6 months after exit. There are also possible concurrent localised risks: transport or staff disruption, severe winter weather or flu that could exacerbate the existing market fragility, and that cumulatively could stretch resources of providers.


● Certain types of fresh food supply will decrease. Critical dependencies for the food supply chain may be in shorter supply. In combination, these two factors will not cause an overall shortage of food in the UK but will reduce availability and choice of products and will increase price, which could impact vulnerable groups. There is a risk that panic buying will cause or exacerbate food supply disruption.

● Public water services are likely to remain largely unaffected. The most significant single risk is a failure in the chemical supply chain that might affect up to hundreds of thousands of people. In the event of a supply chain failure, or the need to respond rapidly to other water supply incidents, urgent action may need to be taken to make sure people continue to have access to clean water.

● Demand for energy will be met and there will be no disruption to electricity or gas, however there will likely be significant electricity price increases for consumers, and wider economic and political impacts.

● Regional traffic disruption caused by border delays could affect fuel distribution within the local area, particularly if traffic queues in Kent block the Dartford crossing, which would disrupt fuel supply in London and the South-East. Customer behaviour could lead to local shortages in other parts of the country.

Low income groups will be disproportionately affected by any price rises in food and fuel.


● Some cross-border UK financial services will be disrupted.


Law enforcement data and information sharing between UK and EU will be disrupted.

Protests and counter-protests will take place across the UK and may absorb significant amounts of police resource. There may also be a rise in public disorder and community tensions.


● UK citizens travelling to and from the EU may be subject to increased immigration checks at EU border posts.

● UK nationals will lose their EU citizenship and, as a result, can expect to lose associated rights and access to services over time.

● UK pensioners, workers, travellers and students will need to access healthcare in different ways, depending on the country. There is a risk of disruption for patients and a minority could face substantial costs.


● Gibraltar, due to the imposition of border checks at its border with Spain, will see disruption to supply of goods (including food), medicines, trans-frontier shipment of waste, and delays of over 4 hours for at least a few months in the movement of frontier workers, residents and tourists across the border.


● The “no new checks with limited exceptions” model announced in March to avoid an immediate risk of a return to a hard border on the UK side is likely to prove unsustainable due to significant economic, legal and biosecurity risks. With the UK becoming a third country, the automatic application of the EU tariff and regulatory requirements for goods entering Ireland will severely disrupt trade.

The agri-food sector will be the hardest hit, given its reliance on highly integrated cross border supply chains and high tariff and non­tariff barriers to trade. Disruption to key sectors and job losses are likely to result in protests and direct action with road blockages.

● There will be significant pressure to agree new arrangements which supersede the day one model within days or weeks.


● EU and EEA fishing vessels could enter illegally, or already be fishing in UK waters on day one. This is likely to cause anger and frustration in the UK catching sector, which could lead to both clashes between fishing vessels and an increase in non-compliance in the domestic fleet.

Read the Operation Yellowhammer in full:

Note that Rosamund Urwin, the Sunday Times’ senior reporter who had had access to the original leaked document in August, has confirmed tonight on Twitter what paragraph 15 (heavily redacted in tonight’s version) actually contains.

Twitter / @RosamundUrwin

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[This is an original piece, first published by the author in PoliticsMeansPolitics.com on 11 September 2019. | The author writes in a personal capacity.]

(Cover: Operation Yellowhammer document.)