THIS is supposedly an age of disruption. Across the world, established giants are being slain by startups fuelled by nothing more than brains and bravado. The most exciting question hanging over Britain at the moment is whether the same spirit can be applied to the country’s ossified political structure.

Rumours of a new political party abound. The Observer has suggested that Simon Franks, a film mogul, has amassed £50m ($70m) to fund a new party. The Times has revealed that David Miliband, a former Labour foreign secretary, is willing to return from New York to offer his services. Sir Nick Clegg, a former Liberal Democrat leader and David Cameron’s deputy prime minister, has hinted that he might join a new party.

It’s easy to see why this talk generates such excitement. Many Britons are repulsed by both Jeremy Corbyn’s hard-left Labour Party and Theresa May’s Brexified Tories. Some 56% tell pollsters that no party represents their views. Moderate MPs from both sides of the aisle make no secret of their contempt for their leaders. Emmanuel Macron, who founded a new party to seize the French presidency last year, provides a model and an inspiration.

Yet the British political system is likely to prove much more difficult to disrupt than, say, the British high street. The first-past-the-post system is hard on startups—Britain has had only one nationally successful and enduring new venture in the past hundred-odd years, the Labour Party—and it is particularly hard on centrist ones, because their voters tend to be evenly spread across the country. The last centrist startup, the SDP-Liberal Alliance, won 25% of the vote in 1983 compared with Labour’s 28%, but only 23 seats compared with Labour’s 209.

People who hope for a great political realignment need to reckon with two obvious problems. The first is that Britain already has a centre party. The Liberal Democrats, the heirs to the SDP-Liberal Alliance, polled only 8% in last year’s election, on a platform of reversing Brexit. The second is that the country is awash with new parties. In the first three months of this year 35 new ones were formed, including one called the Sensible Party.

Those who say the mooted new party would be different point out that it is garlanded with big names. But the names are the very opposite of what you want in a disruptive party: fallen Goliaths rather than plucky Davids. Mr Miliband is Davos Man incarnate (the Times article lauding his reappearance quoted a friend pointing out that the great man is “still attracted to Britain”). Sir Nick is a titled throwback to the Cameron years (perhaps a rule of thumb for breaking the mould is not to give prominent roles to people with knighthoods). The people problem is most acute among the Lib Dems, who are led by a quintessential yesterday’s man, the 74-year-old Sir Vince Cable, and are represented in Parliament by 12 lacklustre MPs and 98 peers.

Britain’s centrists are hopelessly divided over the most basic strategic question: should they upturn British politics by starting a new outfit, or try to reclaim their ancestral parties from within? This debate is most intense in Labour. Moderate MPs tried hard to get rid of Mr Corbyn, only to see him hold onto his job and win 40% of the vote in last year’s election. Now they are restive again, following rows over Russia and anti-Semitism. Some Labour MPs still talk of forming a moderate parliamentary bloc and leaving Mr Corbyn with the hard-left dregs. But the result is likely to be exactly what it was last time: paralysis and drift, while Mr Corbyn tightens his grip on the party apparatus.

The biggest problem for centrism is not practical but intellectual. At the start of the century, centrists were convinced that they had a winning formula: a free market in morals as well as economics, and a determination to use the proceeds of growth to help the poor. This philosophy colonised all three main parties. But today it lies in ruins. The financial crisis has destroyed the centre’s reputation for economic competence. The concentration of wealth in London has undermined its claim to stand for social justice. And social liberalism is alienating conservative voters.

So far, centrists have done a singularly unimpressive job of putting their philosophy back together. This is partly because they are divided: between fundamentalists, who dismiss criticisms of the old model as manifestations of closed-mindedness, if not outright racism; and reformers, who recognise the need to fix the model’s weaknesses. Brexit is also to blame. Many centrists are being driven so mad by the vote to leave that they haven’t got the mental energy to think about why it happened in the first place.

Blame the script, not the actor

Reconstructing this centrist philosophy will be harder than building it was. New centrists need to start by understanding why their philosophy has imploded, which means learning not only why the financial system went into seizure but also why, even before the crisis, so many people felt left behind, culturally as well as economically. They also need to reconcile opposites. How do you remain in the sensible centre while leading a revolution against Britain’s new oligarchy, the clique of second-rate people in both the public and private sectors who have got rich by sitting on each other’s boards and marking each other’s homework? How do you address technocratic questions about the wiring of capitalism (stock options, public listings, takeover rules) while fashioning a compelling vision of a capitalism that works for everyone?

Time spent trying to rethink liberalism is much more likely to be repaid than time spent building a new party. New parties sink into the sand unless they are very lucky. New ideas can colonise old parties and redirect old debates. Beatrice and Sidney Webb said that the best way to change the country was to “permeate” all its parties, left, right and centre, with ideas. Today’s centrists need to do likewise, and focus on thinking up new ideas rather than inventing new parties.