Perhaps the most remarkable element of the government’s unendurably shambolic latest fortnight is that its gravest potential disaster has barely even been acknowledged. It is becoming increasingly likely that the Brexit talks will not advance to the next stage in December. This makes an immediate political crisis, and economic shock, a real prospect. It also renders a deal before 2019 all but impossible. The government, firefighting, crumbling and paralysed, looks away.

How have we reached this point? In short, lack of time and excess of delusion. The most serious EU decisions can only be taken at national leaders’ summits. Given that we wasted three months after article 50 was invoked, the earliest time to kickstart negotiations on our future relationship – and specifically trade – was in October. Theresa May’s Florence speech took Britain some of the way to “sufficient progress” for those talks to begin, but other leaders deemed her financial commitments – and progress on citizens’ rights – still lacking. The next windows for a collective EU nod are now in December and, after that, March 2018. The European parliament must have a draft on which to vote by October 2018.

To be clear: a 10-month negotiating window was stretching credulity, especially given the lack of progress over the past five. But seven months to negotiate the most complex deal in modern European history, even in outline, defies the limits of human capacity. That deal cannot and will not be done.

The consensus in the British government and media has been that talks will indeed be triggered in December. Far less frequently have people asked why. EU leaders were clear in October that the prime minister had to give much firmer commitments on money; May was clear that she had gone as far as she could. Very little seems to have happened since, and indeed, all the signs from London have indicated a government in retreat. Boris Johnson has imposed his own red lines (for example on new EU legislation) and escaped sanction, while David Davis has declared that no new negotiations can take place during a transition period – even though the transition’s fundamental purpose is to do just that. EU officials, meanwhile, suggest that Britain has pulled back from certain guarantees on citizens’ rights.

EU officials are mystified by the UK’s intransigence – and incompetence. Some suspect that senior ministers do not understand the Brexit process, or the consequences of no deal, and are depending on British exceptionalism and pluck to win the day. Meanwhile, the EU’s own red line, from a position of far greater power, remains firm: the government must meet its financial commitments. If it intends to leave what Brussels considers a gaping hole in the EU budget, there will be no second phase of talks in December, March or ever.

The consequences of that outcome are still only vaguely understood in Britain, but will be devastating if they arrive. No deal means that Britain will find itself outside every EU treaty, body and law overnight. Instant sovereignty, perhaps; but also new tariffs, a plunging pound, lorry parks at Dover and the hardest Irish border. Outside the regulations currently governing British aviation, and the Euratom agency, planes will be grounded and radiotherapy drastically curtailed. This is not scaremongering, but a statement of legal fact.

The UK’s unresolvable problem is that Brussels holds each card and thus dictates each decision. The government may find the EU’s stance unreasonable, but this is irrelevant. If the UK wants to play ball, it must, sooner or later, follow the EU’s rules.

If Theresa May knows this, she is unable to admit it. Her political position is so weak that a major concession on money could be unsellable to much of her party and the rightwing press. She is also in no position, yet, to request an extension to article 50, which is the only viable solution and which, according to officials, the EU27 would happily grant. Conversely, the price of doing nothing, which appears to be the current strategy, is infinitely more costly – for both her position as prime minister and, more importantly, the country’s immediate economic future. Businesses and investors – as well as hundreds of thousands of EU citizens on whom the economy depends – have already staked any remaining confidence on a quickly agreed transition. The spectre of a no-deal scenario next month will rapidly drain the dregs of optimism.

It is against this outlook that some senior EU officials are estimating the chance of no-deal at over 50% – while insisting that they will not throw Britain off a cliff unless it really wishes to jump. The government, engulfed by other crises, may of course not survive long enough to reach that precipice. But if it does, our communities, industries and national economy will not survive the fall.

• Jonathan Lis is deputy director of the thinktank British Influence