I leave my job as Leader of the Lib Dems with British politics in a tantalising position: four parties, including mine, seemingly in a tie for public support. It is very likely that this current equilibrium is unstable. The first-past-the-post system may well narrow the field, but it isn’t yet clear how. Where their political strategies have failed, both Labour and the Conservatives will hope desperately that old voting habits and party loyalties restore their threatened hegemony.

But we may get a new form of two-party system, as happened between the wars with the quiet death of liberal Britain. Liberalism is now ready for a noisy revival and resurrection, as a principled counterpoint to the Conservative Party's English nationalism. It's also possible that we may see the irreversible implosion of both traditional parties, with new forces filling the vacuum, particularly on the traditional right.

The outcome is yet unclear. What I do know for certain is how my own party came back from near death to become a major player once again. I was part of the disastrous election in 2015 and lost my seat together with over three quarters of my colleagues. The popular narrative of the left – that this was the public’s reaction against the Coalition and austerity – was, at best, only a small part of the story.

The bigger truth that explains the swing to the Conservatives was the fear in middle-class England of a socialist government propped up by Scottish nationalists. That fear is still alive, and Conservative spinners will build up the prospect of a Corbyn-led government – however improbable – to horror proportions. It is the one thing that gives the Tories some continuing hope of uniting their party.

Condescending opponents explain the Liberal Democrats successes this spring – 700+ gains in council seats and a big advance in the European elections – as the result of sheer luck and protest votes. No doubt this played a part. But I don’t think I am being too self-congratulatory to say that I – and to give proper credit, my predecessor Tim Farron – got some big things right.

The first was the rather obvious, but frequently overlooked, understanding that you build or rebuild a party, like a house, from the foundations up rather than from the roof down. We have spent most of the last few years re-establishing what we – rather grandly – call the infrastructure: the local government base; membership; campaigning and social media capacity – without which a party is just an abstraction or a vanity project.

When I returned to parliament in 2017, it was painfully clear that the Lib Dem leader, I discovered, is allowed to ask the prime minister a question once every four weeks; the SNP parliamentary leader has two a week; the Labour leader six a week. The main media channels take their cues from parliament. After spending hours trying to “catch the Speaker’s eye” for the privilege of addressing a dozen MPs, nestling in a catatonic state catching up on lost sleep, I realised that I would be more use outside of Westminster.

When the question was asked “Where is Cable?”, I was usually found on the way to meet and encourage active supporters, or at a party dinner to raise a few hundred pounds to finance a leaflet. I would return to frustrating encounters with potential backers demanding a “vision” and to “be inspired”, and an explanation as to why I couldn’t metamorphose, with the help of their millions, into a British Macron.

Such naïve thinking led to the political cul-de-sac of Change UK, Renew, Unite for Change, and similar projects. I confess to a few uncomfortable months while the mania for such new parties seemed to offer real competition. Meantime, the Lib Dem guerrilla army was being quietly reassembled and was winning hand-to-hand local battles around the country, mostly unreported.

A series of much bigger battles arrived in May, in which the party soared. My successor will have some hardened fighters alongside her to build parliamentary campaigns against the Conservatives, and then to advance elsewhere, including in Labour’s complacent northern city strongholds – which we ran once, and will do so again.

The second good call was to be right and clear on the big issue of the day: Europe. The referendum occurred when I was out of parliament. It seemed at the time blindingly obvious that there was a sensible compromise to be had around a “soft Brexit”, keeping the economic Common Market while exiting political integration.

That was to underestimate the Conservatives’ obsessive need to generate unnecessary fights over Europe, leading to the disastrous “red lines” at Lancaster House. My predecessor and his colleagues were smart enough to see a gap in the political market for a party that was credibly unambiguous about the merits of staying in the EU. The strategy took time to bear fruit, but I didn’t need much persuading that we should embrace it. Whatever Johnson now does, the strategy will remain relevant; there will either be a “betrayal” of a May-style deal or a very messy, costly, “no deal”. Of course, there is also need for a liberal and social democratic agenda beyond Brexit and we have plenty of substance to draw on in economic policy, the environment, education, health and housing. The party is prepared for a general election at any time.

Third, and not least, there has been an understanding, based on long and painful experience of the parliamentary and local voting system that insurgent parties, rather than suffer the narcissism of small differences, must collaborate. We have worked with the Greens at the local level, not least in my own home Council of Richmond, and in Layla Moran’s Oxford patch. Divisive habits die hard; I read recently that, among my more minor failings, I had murdered hundreds of thousands of children: a breathless accusation from Greens with whom we agree on most of the major issues. Yet collaboration is happening, and will deepen in the future.

Jo Swinson has every reason to be optimistic about the prospects of the Lib Dems. We go into the next General Election with every chance of winning large numbers of seats. There is also the prospect of teaming up with likeminded Labour and Tory MPs who will, by then, have given up on dysfunctional parties of extremes. We will then be reading about the quiet, or not so quiet, death of another great party, and the rebirth of our own.