To a time traveller from the post-war era, Britain today is a fundamentally different place from what it was. All the old certainties are gone.

Few people expect to have a job for life, a third of marriages end in divorce within 20 years, nearly a fifth of the population was born abroad and Christianity is fast becoming an anachronism.

We should hardly be surprised when our political system, designed for an entirely different nation, stops working. And last week, spectacularly, it did.

In the wake of disastrous local election results for Labour, an internecine war broke out at the highest levels that has shocked even Whitehall veterans by its levels of personal vindictiveness.

In a speech on Saturday, Wes Streeting called for a ‘proper contest’ to replace the Prime Minister in his first public appearance since resigning as Health Secretary.

With Andy Burnham, the mayor of Greater Manchester, announcing he will fight a by-election in order to stand for the Labour leadership, and ex-deputy prime minister Angela Rayner waiting in the wings, we are now faced with the grim prospect of a long and drawn-out battle for the succession.

And this whirling political carousel has become actively dangerous to the general public.

As Labour’s finest pursued their personal ambitions last week, gilt yields went up – City speak for the rise in the cost of government borrowing – and the pound plunged.

Meanwhile, oil price hovers above $100 a barrel as the Strait of Hormuz remains blocked, with all that means for energy prices and the cost of living.

At a time of mounting international tension, a country in crisis needs the smack of strong government. Instead, our politicians are fighting like ferrets in a sack.

If Starmer falls – and his long-term survival chances look non-existent – the UK will see its seventh prime minister in less than a decade.

Given the political life expectancy of the average modern PM, the famous black front door of No 10 might as well be replaced with a revolving one.

Since the departure of David Cameron in June 2016, Theresa May, Boris Johnson, Liz Truss and Rishi Sunak have all been in and out again. The only constant during their tenures has been Larry the Cat, who has been in post for 15 years since arriving in 2011.

The epic reigns of Margaret Thatcher (11 years) and Tony Blair (ten) are unlikely ever to be repeated. In 2018, former Labour PM Gordon Brown predicted politicians in the future would have a maximum ‘shelf life’ of six years.

‘People get bored very quickly with the personalities,’ he said. ‘They get fed up with you, they’ve had enough, they’ve seen it all before, because of the 24-hour nature of news.’

He is right, of course, that the modern media landscape has made life much more difficult for today’s politicians than it ever was for their forebears.

First, the arrival of round-the-clock TV news channels created an ever-increasing demand for ‘content’, with politicians under pressure to respond immediately to the most trivial developments.

Meanwhile, the rapid rise of social media has given even the most minor backbencher a platform to promote their favoured candidates, do down opponents or stoke controversy.

Few can weather such relentless scrutiny for long. Indeed, Gordon Brown’s prediction now looks uncharacteristically optimistic. The lesson of last week’s results is that, come the next general election, we face a multi-party future at national level, too.

And that means we can look forward to a new political era marked by horse-trading, coalition infighting and snap elections called by exasperated prime ministers.

Our fractured future is a reflection of the increasingly incohesive country that Britain has become.

Mass immigration has radically altered the national demographic. Whether our leaders admit it or not, the deep-rooted anxiety over the influx of millions from other countries underlies much of our current political discourse, and was probably the most significant factor in the Brexit referendum.

But the failure of governments to deport migrants in significant numbers since voters supposedly ‘took back control’ illustrates another truth about modern governance: It has become circumscribed by outside forces. International laws and conventions, primarily the European Convention on Human Rights and the UN Refugee Convention, mean it’s almost impossible to make the threat of deportation a meaningful deterrence.

This usurping of ministerial power means government is more impotent than ever, its executive powers ceded not just to the judiciary but the civil service, regulatory bodies and quangos such as the Office for Budget Responsibility.

It doesn’t help that the quality of our political class has never been poorer. This would be less of an issue if we were enjoying a period of unparalleled peace and stability. Instead, we are living in a time when living standards have barely improved for 20 years – the longest stretch in British history – and conflicts in Ukraine and the Middle East are having a significant impact on the global economy.

The pace of change has never been so dizzying, with leaps in digital technologies emptying our offices and ending the daily commute, as the ‘work from home’ phenomenon takes hold.

And Artificial Intelligence is set to disrupt the way we do business in almost every sphere imaginable.

Unlike the economic revolutions of the past, however, our current one has not brought us prosperity.

The UK’s tax burden is now at its highest level in over 70 years, the interest on our £2.9 trillion debt mountain is costing us £110 billion a year and inflation is running at 3.3 per cent, well above the Bank of England’s target of 2 per cent, and set to rise even higher.

Labour appears wedded to a redistributive socialist agenda that will compound these problems. And the burden of paying for this is falling disproportionately on the young. Pensioners have doubled as a proportion of the population since 1951. More than 13 million people now draw the state pension, compared with 4.8 million 75 years ago.

Thanks to social media, more people are aware of politics than ever before, but their knowledge is shallow, shifting and often devoid of genuine experience. They want change and they want it now.

New worlds are born out of epochal shifts. Following the end of the Napoleonic Wars, Victorian Britain created an empire on which the sun never set.

This was brought to an end by the Second World War, which spawned a new era that saw the emergence of the big state and the growth of supranational institutions. That settlement – the one into which I was born – is now going through its death rattle, and our current political chaos is a symptom of its demise.

It seems clear that, in time, a new order will emerge. Whether it is a golden age or something else entirely, only time will tell.

l professor Robert Tombs is the author of The English And Their History, published by Penguin.