For the first time in centuries then, a French leader has the chance to either throw a British prime minister a rope or cut her adrift. The stakes for Britain could not be higher: Its decades of membership in the EU mean that leaving the single market would severely disrupt its economy. Its supply chains are so integrated with Europe’s that simple “third country” border checks on goods imported into the country would cripple entire industries built on “just in time” deliveries of components from the Continent. This is why May is desperately seeking a compromise that would allow Britain to stay in the single market just for goods. But the EU’s position—that Britain should accept the full terms of single-market membership, including the free movement of labor—has effectively ruled out the Chequers plan.

Britain’s Gordian knot is May: She promised to implement the result of the 2016 referendum, explicitly interpreting it as a demand to end free movement. Downing Street has warned Germany and above all France that compromise is necessary to stave off a potentially catastrophic “no deal” Brexit. Such an outcome would see Britain crash out of the bloc without an agreement, throwing havoc into complex supply chains, border crossings, and financial flows across the Channel. To many in Paris, this sounds like blackmail.

But May appears to have little chance of convincing Macron to back the Chequers plan. Those familiar with his thinking have told me he views the threat to the single market stemming from any breakup of the EU’s cherished “Four Freedoms”—the free movement of goods, capital, services, and labor—as existential. Britain must accept all of the Four Freedoms, including the free movement of labor, if it wants to preserve the free movement of goods, those familiar with Macron’s thinking have told me. This, they said, is because Macron feels that the EU is too fragile to offer Britain a special deal allowing it to cherry pick which one of the Four Freedoms it wants.

France’s own populist menace plays a role here. British officials have failed to grasp that Macron views the EU’s redlines against Brexit as a necessary warning to anyone else wishing to break up the bloc—as a means of dissuading anyone at home from thinking Frexit is even a remote possibility. For Macron, being tough on Brexit is being tough on Le Pen. Conversely, a flurry of his opponents on the right who want to undermine the European Commission have called for a compromise.

Despite this, British officials have frantically pointed to the precedent of Switzerland, or the Channel Islands, or the EU’s own backstop plan for Northern Ireland, where compromises on the Four Freedoms have been made, to suggest that the Chequers plan could work. French officials, just like Barnier, continue to dismiss these ideas, politely reminding the British that the EU chief negotiator is not his own free agent, but the representative of the EU’s member states. In an ominous statement yesterday, the Élysée emphasized that the Brégançon meeting was not a negotiation and no substitute for talks with Barnier.