Last week saw the third release of leaked documents from the Integrity Initiative and the Institute for Statecraft. Among them were what appear to be the minutes from a private discussion between the Institute and General Sir Richard Barrons – a former British general – that took place just over two years ago.

While common sense, its conclusions are broadly unacknowledged in political debate. That such an obvious diagnosis is beyond the realm of acceptable conversation makes it all the more powerful.

“The UK defence model is failing. UK at real risk” reads the top line. The document proceeds to list economic malaise, wartime interest rates and rising inequality as contributing factors to the present situation. Others are longer term including climate change, societal ageing, resource shortages and the shift to a multipolar world.

Most troubling of all is that while many are global in nature, the overwhelming sense is that Britain is particularly vulnerable.

Take the last few weeks of parliamentary chaos at Westminster. A now favoured, and entirely justified, refrain of the Labour leadership is that Theresa May is in government but not in power. With support from the DUP increasingly absent, it appears Mrs May no longer commands a majority in the House of Commons. This is particularly true for the most pressing issue of the day: Brexit.

This was intuited by the Tories last year when they decided their minority government would pursue a legislative agenda so minimal that beyond leaving the EU, it barely exists. Consequently there was to be no state opening of parliament in 2018, only the second time that had happened since 1925.

Now, in addition to lacking executive power, May finds herself held in disdain by many of her own colleagues. While she prevailed last week, winning a vote of confidence by 200 votes to 117, that result presented the worst of all worlds – more dissenters than anticipated and the party being lumbered with the prime minister for a further 12 months. That’s why Jeremy Corbyn’s move to submit a vote of no confidence in her yesterday was the right one.

Under normal conditions a general election would now be inevitable. Now, however, it’s unlikely a new vote will come to pass – primarily because Corbyn would be May’s likely successor. So far this has sufficiently dampened internal hostility within the Conservative party, despite huge divides on Brexit, alongside the fact none of the pretenders want the poisoned chalice of negotiating departure from the EU. Were Ed Miliband or Owen Smith the Labour leader, one of two outcomes would have transpired by now: a successful cross-party consensus on a ‘soft Brexit’ or, failing that, May would have been ousted.

All of which contributes to a mounting constitutional crisis. At this point the sovereign, who still has weekly meetings with the prime minister, is meant to ask whether she commands a parliamentary majority. As Mrs May clearly does not, a course of action would be pursued. This would either entail a new government or fresh elections.

For all the talk of the 21st century presenting unique and unprecedented challenges, from automation to resource depletion, what’s increasingly obvious is that Britain lacks the institutions to not only deal with the future, but the present too. That an unelected 92-year-old is invested with such power in a time of crisis is plainly absurd. The ‘unwritten’ English constitution, so long venerated for its enduring success, is compounding Britain’s problems rather than addressing them. Things will only get more unstable from here.

It’s a similar story in making sense of Brexit. The British establishment wants to remain in – or stay close to – the EU. That’s not to say those who campaigned to leave, such as Boris Johnson, Nigel Farage and Jacob Rees-Mogg, are not establishment figures. Rather they should be viewed as a historically weaker fragment of the larger ruling elite, a minority who have been gaining in traction since the late 1980s and who, even to their own surprise, emerged victorious two summers ago.

The Confederation of British Industry, TUC, Financial Times, Institute of Directors and every major political party wished for Britain to stay in the EU. The only dissenting institutions of any gravity were the Daily Mail and the Sun newspapers.

Brexit is therefore best understood as an internal rift within the ruling class: the patrician establishment – Michael Heseltine, Tony Blair, John Major – on one side, and those fully bought into British exceptionalism on the other. It’s for this reason that a second referendum seems so likely.

Between such a fracture and legacy institutions making the situation even worse, it’s clear the only the block capable of managing Britain, and then re-making it, is one led by the Labour party, the trade unions and the organised left. For them to acquire domestic hegemony, however, will require parts of the liberal intelligentsia and non-urban working class. This is precisely why creating a workable Brexit coalition is so important. It’s the ultimate prize – valuable as it is improbable.

To accomplish this it must find solutions fit for the era. These must not be focused purely on the economy nor wilfully incremental – the successful path of Corbyn’s Labour so far – but a project of modernisation and renewal. How does Britain act in a genuinely multipolar world in a manner which is socially just and breaks with a centuries long legacy of imperialism? How does it overhaul a broken constitutional system where an unelected 92-year-old is invested with more political power than millions? How does it mitigate climate change while ensuring greater social justice? And how is it to contribute to a broader shift in a global order which intentionally under-develops the Global South through a rigged system of trade?

What the last week demonstrates is that however significant you viewed the scale of the challenge facing Labour, it was likely an underestimate. Not only does the British left have to break with neoliberalism domestically, it will have do so in a volatile world order and with domestic institutions in breakdown. The political crisis of the union is a once in a lifetime event, as is Brexit. It’s a similar story for our decade long economic malaise. Meanwhile a government without power at Westminster reveals a constitution in need of radical overhaul – much as it has been for the last two hundred years.

The idea that staying in the EU would solve all or indeed any of these is fantasy – although some might submit it is a start. What’s certain is that only Labour can lead the coalition required to transform the country. A historic re-forging of Britain’s economy is inevitable – that much Labour gets. But the same applies for its culture and political institutions too. Until the latter is grasped the former is impossible. That means a written constitution, abolition of the House of Lords, the sovereign no longer holding formal political power and a revival of national democracy.

If the Greens, SNP and Liberal Democrats wish to side with Mandelson, Campbell and Blair against that then so be it. They too will be dragged down.