A decade ago, liberalism appeared to have triumphed in British politics. The three main party leaders all subscribed to versions of this philosophy. Tony Blair, David Cameron and Nick Clegg shared a belief in free markets, personal freedom and liberal globalisation. Though differen­ces endured (such as over EU integration), what united them was more important than the divisions. Those outside this consensus – the Labour left and the Tory right – were regarded as irrelevant and outmoded.

But liberalism’s victory proved to be a false dawn. In the UK as elsewhere, its adherents have been cast to the margins. The election of Jeremy Corbyn as Labour leader and the vote to leave the EU were, in different ways, repudiations of liberalism. Corbyn rejects the free movement of capital; the Brexiters reject the free movement of people. Once treated as ideological curios, socialists and nationalists hold greater sway than they have done for decades.

No party better exemplifies the retreat of liberalism than its chief exponents: the Liberal Democrats. Having co-led the UK government from 2010-15, they now hold just eight seats (the same number as Northern Ireland’s Democratic Unionists). The greatest struggle they face, senior figures say, is simply proving their relevance.

This month, Nick Clegg, the most notable Lib Dem survivor, published a reflection on liberalism’s crisis – Politics: Between the Extremes. “Of all of the reasons, the one that I think is by far the greatest is the knock-on effect of the 2008 financial crisis,” the former deputy prime minister told me shortly before his party’s conference in Brighton. “Millions of people, quite understandably, and in many ways quite rightly, feel that they’ve been overlooked. Their wages have stagnated, they don’t feel they’re getting a fair slice of the cake. They feel that commercial and political elites don’t understand that grinding feeling that you’re treading water and dealing with the consequences of a crisis that wasn’t of your making. It’s very rich territory for people on left and right to entice voters with very simple solutions to quite complex problems.”

Immigration is often cited as the primary cause of Brexit. The Blair government’s ­decision not to impose transitional controls on eastern European member states is spoken of as a fatal error. But Clegg rejected this analysis. “The concern about immigration is as much symptom as it is cause. If you look at the way people voted in the referendum, some of the areas that cited immigration as their principal motivation for Brexit were also areas where there are the lowest levels of immigration.”

It was far more important, he said, to address stagnant wages and the housing shortage. Clegg has become “ever more statist” on the latter. “If we were, as a country, to resolve that we were going to give central government both the authority and the means to enforce a huge and sustained housebuilding programme over several years, I think that would do more to deal with the underlying sense of disenchantment than any amount of fiddling around with net immigration numbers.”

The Liberal Democrats’ poll ratings remain frozen around 8 per cent. Meanwhile, Corbyn is poised to be re-elected Labour’s leader. And, among the Conservatives, some have been alienated by Theresa May’s opposition to free movement and support for new grammar schools. The answer, it is increasingly argued, is for liberals from all three groups to found a new party, untainted by association with the ancien régime.

Clegg cautioned against this approach without entirely dismissing it. “It’s not as simple as a game of Blue Peter, when you produce a shoebox with some holes in and say ‘voilà’. Not least because we have an electoral system which is so unforgiving to new market entrants. Having said all of that, I do think there is a very compelling case for small-l liberals in the Conservative Party, in Labour and in the Liberal Democrats to work as closely as they can together . . . We do need to caucus and collaborate and compare notes. Where that leads? I think one should start at the beginning of the process, not second-guess the end of it.”

Rather than an era of hung parliaments, as originally anticipated, most now expect a sustained period of Conservative rule. But Clegg suggested that the coalition politics of 2010 could be revived. “If, as I think is perfectly possible, this government drives itself into the buffers because it has absolutely no idea how to fight its way out of this Brexit paper bag, there may well, in a few years, emerge once again a real appetite for a government of national unity: different people of different parties putting the national interest first.”

If the UK’s vanquished liberals are to ­recover, it will be by campaigning on those issues – the NHS, the housing crisis, low wages – that unite cosmopolitans and communitarians. Though Clegg’s party and Labour are historically regarded as rivals, their fortunes have more often than not been intertwined. In 1997, 2001 and 2005, a healthy centre left (and waves of tactical voting) locked the Conservatives out of office. In 2015, Liberal Democrat failure was not accompanied by Labour success. Both parties flourish when their main opponent – the Conservatives – is weak.

Clegg spoke of the potential to exploit the difficulties that the Tories acknowledge they will face. “We are now back to the more comfortable, and perhaps more fruitful territory, of being an insurgent party again. We are now governed by a Brexit establishment.”

The hope for Nick Clegg and others is that an increasingly promiscuous electorate will eventually work in their favour. In a democracy, no party rules in perpetuity. But, as the Corbynites and Brexiters can testify, it could be a long wait.