Britain once exported parliamentary stability as confidently as it exported the Westminster model itself.
Today, it struggles to keep a prime minister. Theresa May could not deliver Brexit. Boris Johnson squandered public trust through scandal. Liz Truss destroyed her premiership with an economic experiment that unravelled within weeks. Keir Starmer, elected with a commanding parliamentary majority in 2024 and expected to restore stability, has left office in under two years. It is tempting to attribute this extraordinary turnover to a succession of flawed leaders. That, however, mistakes the symptom for the disease.
For much of the post-war era, Britain’s political system rewarded continuity. A disciplined two-party system, cohesive parliamentary parties and an electoral model that routinely translated votes into durable Commons majorities gave prime ministers the authority to govern. Margaret Thatcher and Tony Blair each remained in office for a decade. Britain is now poised to appoint its seventh prime minister in a decade. Such instability is no longer an aberration. It has become a defining feature of British politics.
Brexit undoubtedly accelerated this decline. It fractured party loyalties, hardened political identities and forced governments to navigate competing visions of Britain’s future. Social media has amplified polarisation and rewarded ideological absolutism. Yet neither phenomenon adequately explains the collapse of prime ministerial longevity. Other democracies confront similar pressures without experiencing such relentless leadership churn. Brexit intensified Britain’s instability. It did not create it.
The deeper transformation has occurred within parliament itself. Prime ministers exercise authority only so long as they retain the confidence of their parliamentary parties. Throughout much of the twentieth century, party discipline largely shielded leaders from internal revolt. Since the 1970s, however, MPs have become increasingly willing to challenge, undermine and ultimately remove their own leaders.
The Iraq War profoundly weakened Tony Blair’s authority within Labour. David Cameron’s decision to hold the Brexit referendum was itself a concession to years of Conservative rebellion over Europe. Boris Johnson did not fall because voters rejected him but because Conservative MPs concluded that Partygate had made him electorally toxic. Starmer’s welfare reforms and tougher immigration policies similarly forced Labour MPs to choose between political loyalty and political survival.
The consequences are striking. The last prime minister to enter Downing Street after winning a general election and leave office after losing one was Edward Heath in 1974. Since then, British prime ministers have increasingly been removed by colleagues rather than by voters. The office has become constitutionally powerful but politically fragile.
This fragility has been reinforced by a second structural change. Britain’s electoral landscape is no longer dominated by two stable parties. Scotland remains shaped by the constitutional question. Northern Ireland continues to operate through its own political logic. In England and Wales, Labour and the Conservatives now face growing competition from Reform, the Greens and Plaid Cymru. Electoral loyalties have become weaker, coalitions more fragile and political volatility the new normal.
These changing incentives reshape parliamentary behaviour. MPs representing increasingly competitive constituencies have little reason to stand by an unpopular leader in the hope that public opinion will recover. Their political survival depends upon acting before the electorate passes judgement. Leadership challenges have therefore become instruments of electoral self-preservation rather than exceptional constitutional events.
Britain has consequently entered a vicious cycle. Fragmented electorates produce anxious MPs. Anxious MPs weaken prime ministers. Weakened prime ministers struggle to govern. Governmental failure further fragments electoral loyalties and deepens parliamentary insecurity. Every failed premiership lowers the threshold for removing the next. Leadership changes, intended to restore stability, now accelerate instability instead.
Andy Burnham inherits precisely this predicament. His record as mayor of Greater Manchester has earned him a reputation for pragmatic administration and effective political communication, while Labour’s improved performance in the Makerfield by-election offers cautious grounds for optimism. Yet personality cannot resolve structural dysfunction. If Burnham retains Labour’s tougher immigration agenda, fails to deliver meaningful public control over key services or simply experiences the inevitable erosion of political popularity, he will confront the same parliamentary arithmetic that consumed his predecessors.
The central question, therefore, is not whether Andy Burnham is a more capable politician than those who came before him. It is whether any prime minister can restore durable authority within a political system that has steadily eroded the conditions that once sustained it. Britain’s revolving-door premiership is neither an accident nor merely the product of flawed individuals. It is the consequence of a political order in which fragmented electorates, insecure MPs and increasingly disposable leaders reinforce one another. Until those structural incentives change, the occupant of Number 10 may change often, but Britain’s instability will endure.
The writer is a lawyer and political commentator.
