“Theresa May and David Davis have provided a case study of grotesque uselessness” in their approach to Brexit. This comment was not made to Prospect by one of the usual “Remainer” suspects, but by Dominic Cummings, the Vote Leave mastermind.

Negotiations with the EU are in a dire state. Britain faces its biggest constitutional challenge ever—and is on the verge of cocking it up. Cummings, the official “Leave” campaign’s former director and long-term aide to Michael Gove, is extremely clever—but comes with a reputation for being a little too-clever-by-half.

He has written online treatises, running to many thousands of words, on the careful calculations that inclined him to think that—on balance—Britain was better off taking the punt on Leave, and the thinking behind his ruthlessly effective campaign. He has been withering about David Cameron, ridiculing him as “the guy in No 10 watching Netflix with a glass of red in his paw,” and is no politer about May today. “It was crazy” of her “to trigger Article 50 without preparations first and even more crazy to sit around and still not prepare,” he said. “If there’s no deal, there will be significant problems that were completely avoidable.”

And the thing is, he’s right. Six months have passed since Article 50 was triggered, but Britain and Europe have reached agreements on almost nothing. We simply aren’t getting anywhere. The PM’s Florence speech was designed to unlock talks, but it did not. In early October the European Parliament decided that insufficient progress had been made in the talks and that negotiations could not move to their next phase. Massive policy gaps still remain. A deeply divided government finds itself unable to close them, and while various senior ministers say preparations are underway for a “no deal” scenario, this is hardly reassuring. Not when the government won’t publish them—and when a cliff edge outcome would damage Britain’s economy so severely.

Not everyone’s panicking. At a “Leave means Leave” event at the Conservative Party conference in Manchester, Owen Paterson, a prominent Eurosceptic, looked with glee over the cliff edge: “If the European Union is still messing around by Christmas,” Britain should “give notice, on 1st January, that we will be moving to WTO rules.”

This would be a catastrophic error. Paul Daly, a Fellow in Law at Cambridge, tells me that a no-deal outcome “would lead to economic chaos.” The UK “would adopt, overnight, third-country status in the eyes of the European Union.” The result would be mayhem. “Planes would not take off, nuclear fuel would not be imported and haulage traffic to the Continent would grind to a halt.” The man who drafted Article 50, John Kerr, also told me recently that “flights in and out of continental Europe [will] stop unless we negotiate some replacement for the regime we’re members of.” It’s no exaggeration, then, to say that the new Brexit Britain that is supposed to be soaring into the skies would find itself grounded on the tarmac.

No wonder Cummings is so worried—this epochal diplomatic screw-up could quite easily happen. The government’s Repeal Bill is supposed to take all EU law into UK law, but as Daly points out, even if we’re still “fully convergent with EU law… Belgian customs officials, French financiers, Italian importers… will not recognise the UK as part of the EU trading system.” They won’t be allowed to. The Repeal Bill fills the domestic legal vacuum, but without a deal with Europe, our “current trading arrangements will fall into a void.”

Nor is the idea of falling into the arms of a newly-cosy trading relationship with America looking so convincing after the US slapped hefty tariffs on Bombardier and jeopardised jobs at the aircraft manufacturer’s plant in Northern Ireland. In truth, it was never going to work. Peter Chase, who spent years promoting transatlantic trade at the US Chamber of Commerce thinks US trade is never going to compensate because Europe is “a huge economy right on your doorstep…” If that conclusion wasn’t chilling enough, he added: “The US companies that have invested $580bn into the UK did not do so to serve the English market. They did so because they saw the UK as a platform into the EU.” In other words, Brexit could actually end up weakening our economic links with the US. None of the Leavers’ bluster was really thought through.

Am I being unduly alarmist? I hope so. Britain and the EU could and should wind up striking a free trade deal. Certainly, that is what some committed Leavers were saying in Manchester, where Andrea Leadsom ridiculed claims it would “take eight to 10 years to strike an FTA” as “nonsense!”

But such faith in the current administration’s ability to haggle effectively seems complacent. The far-sharper Cummings was not nearly so sanguine. On May and Davis, he predicts that “schoolchildren will shake their heads in disbelief that such characters could have had leading roles in government.” In the event of a total Brexit disaster, there could even be an investigation into why it occurred—and civil servants are already scurrying to cover themselves. Officials are drafting their emails with a half an eye on “the inevitable inquiry,” Cummings said—“and the history books.”

Cummings, of course, has already earned a place there as the brains of Brexit. This week we learned that he has deleted his Twitter account. I wonder if he’d like to see Brexit erased too.