Eight weeks ago in this newspaper, I laid out an argument as to why those who were sceptical about Jeremy Corbyn’s leadership should pull together and support Labour candidates across the country.

Like so many others, I thought we were in for a heavy defeat and that unity was the only way to save the Labour party from a catastrophic wipeout. I was wrong.

Not only did Corbyn’s campaigning zeal enthuse so many young people to vote, but created a motivation and clear anti-austerity alternative to the Conservatives, which captured the imagination of many and the net gain of 30 seats.

One of my contributions to the campaign was in an unexpected quarter in the Sun on Sunday. I found myself reflecting that an alternative approach to political campaigning might, as it did with Clem Attlee, lead to unexpected outcomes. Little did I know quite how substantial that reversal of fortunes might be.

So, congratulations to Jeremy, but congratulations to all those dedicated workers, to our candidates and, yes, to the Labour party’s paid officials, who ran the campaign on the ground. As so many others, I sought to make my contribution, which is why I found the comments of Len McCluskey, general secretary of Unite, so dispiriting in the days after the general election outcome.

A moment’s thought might have led him to understand that the situation we experienced in the local elections at the beginning of May shook everyone. Compromises were necessary on all sides, including the manifesto itself, and that a basic and old-fashioned commitment to unity and fraternity prevailed.

That is what is needed now. An understanding that the largest proportion of the popular vote since 2001 and the greatest uplift in the popular vote since 1945 give us a real base to go forward. But forward together, not in either an atmosphere of revenge or an Alice in Wonderland detachment from reality.

We have a mountain to climb and climb it together we must. We are 64 seats from an overall majority of one. We have four more seats than we had in 2010, but this time we have 12.8m votes and 40% of the popular vote.

We have, in short, returned to a two-party system in England and Wales and a diminished standing of the Scottish Nationalists.

And anyone (and in my role as professor of politics in practice at the University of Sheffield, I have) who has examined the nature of the political arithmetic will know that once you have mopped up most of the left and left-of-centre votes, the challenge to win over sufficient Tories becomes even greater.

Retaining and building on the votes of young people who have never voted in such large numbers before is crucial to future victory. But we also need to regain the votes of those older members of electorate who either deserted us to the Tories, whose vote after all went up, or who abstained.

The catastrophic mistakes of the Conservatives, now reinforced by their alliance with the Democratic Unionist Party, aid us in this endeavour. The Tory party in alignment with the DUP is for many young people a deeply unattractive prospect.

Ironically, what seems to so many people to be “our victory” on 8 June is likely to reduce substantially the less acceptable and therefore unattractive parts of the Conservatives programme. As so often with those of us on the left of politics, it is possible to see a partial victory in changing the landscape within which policy is made, only to see the more substantial victory of a return to power slip away.

In the absence of an early general election, bearing in mind that the Conservatives know everything about how to hang on to power, the time we have must be spent on addressing this paradox. In the absence of a third party in England and Wales capable of garnering disaffected Tory voters, a two-party contest requires Labour to win Tory votes to achieve the real prize of being in government rather than glorious opposition.

To succeed, young and old, radicals and revisionists must find a new accommodation. After all, the challenge to social democracy here and across the world remains – to maintain the support of the enthusiastic new voter, the urban middle class, while retaining and winning further still the disaffected and alienated working-class vote that lost seats such as Stoke South, Walsall North or Derbyshire North East.

It is right for us all to take comfort in, and gain a resurgence of hope in, the taming of Theresa May. But we must never forget that glorious defeat is never the same as victory. In the coalition that has always been the Labour party, we need to hear each other, sometimes hug each other and, above all, have the humility to acknowledge that being right can sometimes turn out to be wrong.