The UK’s strategic orientation in the world is rarely the most salient topic of national debate, and it is lost almost entirely in the mostly domestic politics of quarantine. But coronavirus changes the international context in which Britain operates as a power – large by European standards, but not an equal to the US or China.

The world into which Boris Johnson thought he would be launching his country on exit from the EU is not the one in which it is now adrift. Borders have closed; trade is disrupted; blame flies between nations and regions. Tension between Washington and Beijing simmers close to boiling.

Even before Covid-19, UK foreign policy was warped by delusions of national grandeur. Mr Johnson’s plan was for Britain to be a champion of international free trade, thwarting protectionism by the power of its open-market example. These delusions can be seen in the plan for minimal border checks on trade between Great Britain and Northern Ireland. Eurosceptics hailed the recovery of Britain’s seat at the World Trade Organization as if it were a sovereign crown. In reality, that restoration is no compensation for the loss of a seat at European council summits and the surrender of influence over the regulatory architecture of a continental trade bloc. Whatever the UK can achieve in the WTO will be of second order compared with what it must first negotiate in Brussels and Washington, where it is the smaller, and therefore weaker party.

Ministers will never concede that point. Belief in the “Global Britain” mantra is a requirement for advancement in Mr Johnson’s administration. Pragmatic voices seeking alignment with Europe were long ago drowned out. David Frost, Mr Johnson’s chief negotiator, takes a maximalist position that sees any accommodation to EU jurisdiction as nullifying sacred principles of Brexit. In that respect, he is more ideologue and politician than diplomat, which makes him ill-suited to the task of brokering a deal.

For Eurosceptic hardliners, the priority is a trade deal with Washington, to which end negotiations are under way in parallel with Brexit talks. For the majority of UK businesses, the European side of the equation needs balancing first, since that is where the greater proportion of exports go – around 45%, compared with around 20% to the US. The Atlanticists argue that those proportions describe a status quo from which Brexit is the departure point; what matters is untapped markets. Trade economists query the wisdom of betting everything on benefits that don’t exist yet at the expense of those that do.

Brexit ultras also think a deal with Donald Trump will put pressure on the Europeans by demonstrating that the UK has options. But Brussels sees Mr Trump’s nationalistic trade agenda as a threat to the stability of the international order. That makes concessions on the European side much less likely. And for some Eurosceptics who share Mr Trump’s wrecking attitude to the European project, maximum damage to relations with Brussels is a goal in itself.

Market access is just one component in this geostrategic contest. Washington wants to dump its agricultural surplus on British consumers (which would ruin domestic farmers), but it also wants the UK to side with Mr Trump in his escalating rhetorical confrontation with China. The EU takes a less belligerent stance towards Beijing. Mr Johnson’s China policy is a muddle, warily engaged, but under pressure from many Tories who prefer the US line.

Meanwhile, the Covid-19 pandemic has incinerated old expectations and savaged economic prospects for probably years. It introduces stresses to an already fragmented global trading order that were not foreseen by Eurosceptic ideologues. It sharpens dilemmas that were already acute. The lone-trade model forces the UK to compromise on two fronts, in parallel negotiations, with little leverage and no allies. Concessions to the east damage prospects to the west. It is easy to see why the prime minister does not want to admit in public that his choices are constrained, not expanded, by Brexit. But it is a fact to which he must adapt to navigate safely through newly turbulent waters.