On Thursday evening, a group of around 20 Labour staffers sat in my front room in Brussels. The clock was about to strike 10.00pm UK time. In a few seconds we were going to hear the results of the exit poll…

Earlier a friend of mine had tweeted me with John Cleese’s classic line from ‘Clockwise’: “It’s not the despair… I can take the despair. It’s the hope I can’t stand.”

I know what he meant. In the previous week, one outlying poll, using a brand new methodology, had suggested that we were on course for a hung Parliament. While everyone else saw a Tory majority as inevitable, YouGov broke with consensus and thought Labour would exceed expectations. It sounded too good to be true. And yet… And yet… It was the hope I couldn’t stand.

We’d been here before, as well. Two years ago, roughly the same group of people had gathered in a bar expecting to see Ed Miliband on his way into Number 10. By 10.01pm, that dream had died. A year later, we were together again to see if we had done enough to convince British voters to stay in the EU. The polls were neck and neck, the hope was there… and then, once more, it was dashed.

So you could forgive us for clutching our glasses tightly, teeth clenched, peering worriedly at the screen as Big Ben sounded 10 o’clock… and the screen turned a familiar Tory blue. “We are predicting the Conservatives will be the largest party,” intoned David Dimbleby. A groan and a resigned sigh around the room. It had happened again.

And then a small voice of hope from somewhere at the back: “Hang on: ‘largest party’? So they haven’t got a majority? It’s a hung parliament?!” A few seconds for this to sink in, and then a huge cheer. They were right! Maybe we were going to do well. Maybe this was going to be a good night!

And it was. Anneliese Dodds, my fantastic MEP boss, turned an impressive 15,000 majority into an astonishing 23,000 one and became the new MP for Oxford East. Labour won back seats in Scotland that were supposed to have been lost for a generation. We held on in Edgbaston, in Exeter, in Ilford and in Hove. Not only that, we won new seats – in Reading, in Plymouth, in Canterbury… in Kensington, for Christ’s sake. The constituency in which the Daily Mail’s office is situated now has a Labour MP!

It was a good night. We stayed up too late, we drank too much and we slept too little. And now, as the dust is starting to settle, I think there are three important things to say.

1. Jeremy Corbyn is owed an apology, and a lot of credit…

I don’t think I’m alone – and I certainly shouldn’t be – in saying that I misjudged Jeremy Corbyn. While I never joined in with, nor approved of, the vehement criticism of him from the moment he was appointed leader, I hadn’t voted for him and I did harbour real doubts about the direction he was taking the party in.

Like a lot of people (including former Gordon Brown adviser Theo Bertram, whose Corbyn mea culpa blog is well worth a read), I thought there were some central truths about how modern political campaigning works. It is infinitely harder, the accepted logic goes, to persuade a non-voter to get out and cast their ballot than it is to change the mind of someone who already votes and bring them over to your cause. Non-voters will only let you down. They’ll come to a rally, they’ll retweet and ‘like’ to their hearts content, they’ll even tell pollsters that they are “definitely” going to vote, but when it comes down to it they’ll stay at home and do something else instead.

We were wrong. Corbyn, and the team around him, saw the untapped potential in a lot of those non-voters (especially the young), decided that the rewards of converting them were worth the effort, and developed a strategy to get them out – by delivering a message of hope, by being unapologetically authentic and honest, and by challenging accepted wisdom rather than being resigned to it. He and his team deserve a huge amount of credit for increasing Labour’s share of the vote by ten percentage points, and our total number of seats by 30. And he of course deserves to keep leading the party and building on this success.

2. But we mustn’t forget that we still didn’t actually win…

Those who harboured doubts about Jeremy Corbyn aren’t the only ones who need to show a little humility, though. Yes, the Labour results of 2017 are a massive improvement on those of 2015. But certain truths are unavoidable.

Theresa May is still the Prime Minister. The Conservatives are still in power. Worse still, they are reliant on the deeply unsavoury DUP to stay there. For all the progress we have made as a party in the last two years, the fact remains that the UK government is likely to continue cutting public services, pushing for a hard Brexit and generally letting down the working people of our country. It’s only when we are actually in power that we can deliver on the promises set out in our manifesto, and reward those who came out and voted for us in the hope of seeing a better society.

So those in Team Corbyn cannot just say that we did really well on Thursday night and leave it at that. We didn’t get over the line.  We fell short, and in some pretty generous circumstances at that. I think it’s safe to say that we are highly unlikely to ever face such an inept, uninspiring Tory party campaign again. They will raise their game ahead of the next election, and we need to as well.  Moving on from New Labour doesn’t have to mean throwing out absolutely everything from the Blair and Brown years. We still need a professional communications outfit; we still need proper message discipline; we still need to think and act strategically. None of those things involve compromising our values. In fact, they’re how we put our values into practice.

3. And we need to start doing some serious thinking…

So we need to build on last week’s good news, and not just rest on it. That means considerably stepping up policy development. The 2017 Labour manifesto was good.  It set out a range of policies which were progressive, popular, and easy to explain on the doorstep. It was an especially impressive document given that the people writing it presumably thought they had another three years to finesse it, before May’s surprise announcement gave them a matter of weeks to get it done.

But it was also quite conservative. It was a long list of promises, with little in the way of an overarching narrative to tell the country who we are as a party. It didn’t have a clear sense of prioritisation – which were our headline pledges, and which were the smaller ones supporting them? The promises didn’t always pass that key test of meaningful politics: that it shouldn’t be difficult for a sensible person to at least set out a dissenting view. If all you’re saying are things that are generally accepted to be reasonable, then you’re not really challenging yourself or taking tough decisions.

The UK faces some immense tests over the coming years: leaving the EU and making our own way in the world; the pressing need to adapt to climate change and end our reliance on fossil fuels (seemingly without the cooperation of the US); the challenges that automation and casual employment pose to working people; our ageing population and the crisis in social care; the new forms taken by stateless terrorism; rebalancing our economy geographically and sectorally; devolving power in a meaningful way. If we are honest with ourselves, we haven’t started to scratch the surface on many of these issues yet.

I don’t mean to take away for a moment from Thursday’s immense, unpredicted success. Jeremy Corbyn’s Labour has earned the right to be taken seriously, to be allowed to carry on with the job and to be treated with the respect due to a powerful political party in the ascendancy. That’s brilliant. But it’s only half the battle. We have to use the coming months and years to show that we are not just a viable, energetic opposition. We need to push on and show that we are in fact the natural party of government.

To use what seems like an appropriate word – we have the momentum. We now have to build on it.