Operation Yellowhammer is the code name for the UK government’s no-deal Brexit contingency planning. The Yellowhammer is a small bird with a distinctive call that is often thought to say “a little bit of bread and no cheese”. Some might think it a sinister reference to the potential impact of a no-deal Brexit on British households (the pattern lines on the bird’s eggs were also once thought to carry a concealed message) – although code names for UK operations are supposed to be generated randomly.

As for the contingency plans, Operation Yellowhammer is being run by Cobra, the government’s emergency committee. Given that how Brexit will happen still remains unclear, contingency planning continues to be essential. It is understood that the implementation of most measures, which was supposed to start on March 25, has been deferred, although there are reports that planning is well behind schedule.

Not much is known about the details of Operation Yellowhammer. There are more than 300 contingency plans across government departments, but the core elements relate to securing critical supplies and keeping traffic moving. Some 3,500 troops have been placed on standby to assist and ferries have been booked to ensure essential medical supplies. There are also contingency plans relating to potential problems for UK nationals who could be stranded in other European countries in a worst-case scenario.

Traffic chaos?

One of the most pressing worries is the potential for traffic chaos around the UK’s main ports as increased checks may be required. This could lead to huge traffic jams in Kent, on the south-east coast, with the port of Dover and Eurotunnel the main connections to continental Europe. Nearly 12,000 trucks on average pass through them a day with around 15,000 on some days. Dover alone handles 6% of UK trade by volume, a much higher percentage by value, and most of this trade is time sensitive.

The UK government has indicated that the bulk of inward trade from the continent would not be subjected to increased checks and that any changed duties from the announced tariff changes could be collected without physical checks at the port. But the traffic chaos in Kent relates normally to outbound trucks and factors beyond the control of the UK government, namely bad weather in the English Channel or strike action in France.

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French customs officials have already demonstrated how well they can paralyse connections to and from the UK by imposing extra checks at passport control. More detailed checks were imposed at ports from March 4 2019 and strike action in the week beginning March 21 2019 caused lengthy delays to Eurostar passengers at Paris Gare du Nord.

Only a small additional delay at the ports can soon produce long tailbacks on the motorways. Operation Brock, one element of Operation Yellowhammer, is due to start on March 25. This will park some of the trucks heading to Dover on one lane of the M20, allowing non-truck traffic to flow on the other lanes, and divert others to a lorry park on the disused Manston Airport so they do not completely block the roads.

But this will potentially still cause traffic chaos on all surrounding roads. The M20 section can hold an estimated 11,000 trucks and Manston can only hold a maximum of 6,500 trucks, barely enough for a busy day’s traffic of 15,000 trucks. Kent County Council issued warnings to schools and care homes about the possibility of shortages of key supplies and the consequences of traffic disruption. Kent Police have also been given £3.5m in extra resources to cover any extra no-deal Brexit costs.

While Kent may be the geographical focus for some of the most obvious problems, there were suggestions based on a leaked government report that queues at St Pancras for Eurostar trains to Paris (where border checks are made by French officials) could be up to a mile long, involving enough people to fill up to four trains, as a result of passport checks holding things up. Services would have to be cancelled to deal with the slow down. This is despite the fact that the European Commission said trains could keep running as normal for three months in the event of no deal.

Prisoner’s dilemma

These problems arise from the fact that most effort has been placed on assuming that there will be an orderly exit from the EU. The political declaration that accompanies Theresa May’s Withdrawal Agreement included a significant “implementation phase” from the date that Britain leaves the EU. This period of around 21 months to the end of 2020 would give space to make the necessary agreement to settle the terms of the future relationship, and plan for factors such as cross-border movements with a greater degree of certainty.

No-deal planning was slow to start because it was thought to be unlikely and potentially a waste of resources. Now the UK is in a situation where, although parliament has rejected a no-deal exit, the UK can still get there by default if there is no alternative that can command parliamentary support.

Plus, even if a no-deal situation is seen to be inevitable, planning for it is difficult when the UK cannot control the actions of neighbouring countries. This looks like a classic case of the prisoner’s dilemma in game theory: which almost always ends badly for both sides. That is, unless the players collude – and that implies a deal, or at least deciphering the markings on the Yellowhammer’s eggs.