For the last generation, despite the twists and turns of Conservative and Labour prime ministers, Britain has been determined to stay at the top table in Europe. Today, David Cameron, after months of posturing and disengagement, took the catastrophic decision to walk away.
We should be under no illusions about the import, the impact or the reasons behind the decision. The significance is that we have chosen to let 26 countries make crucial decisions without us. The prime minister's apparent warning at the meeting that they "couldn't use this building for their meetings" would be laughable if it was not tragic.
The impact cannot be precisely known but the scale of Britain's isolation makes it hard to believe it will not be serious. The reality of the EU is that influence does not always come from rules but from strategic alliances. This government has been left in an alliance of one. And for what? Cameron went into this summit saying his first priority was to protect Britain's financial services industry. Forty-eight hours later it is clear he achieved not one such protection.
Instead, he has delivered the reality that 26 EU countries will now meet to discuss financial services without our country being represented in the room. That is not in the interests of Britain.
And while Cameron tells us he made his decision to protect British business, it is British business that will lose when Britain is not involved in decisions about their largest export market.
The real reasons for this debacle are about internal Tory politics. Even before he entered Downing Street, Cameron pulled Conservative MEPs out of the centre-right grouping in the European parliament. It sent a clear signal he did not want to engage with anyone except mavericks from the extreme margins of European politics. In office, it has got still worse. As recently as March he was telling Angela Merkel he did not even want to be in the room when issues to do with the euro were being discussed. Europe got the message. Last week, when the leaders of centre-right parties in Spain, Germany and France met in Marseilles, Cameron was not invited.
Going into Friday's crucial summit for jobs and growth, at a time of great peril for our country, the British government was bereft of influence and allies.
The truth is that Cameron never wanted a deal at this summit because he knew he was too weak to sell it to his Eurosceptic MPs back home.
When Geoffrey Howe resigned from Margaret Thatcher's government, he complained that in European negotiations he felt like an opening batsman who found his bat had "been broken before the game by the team captain". Today, Cameron didn't even want to be on the pitch. Even before this summit began, he decided to pull stumps and retreat to the Eurosceptic pavilion.
Cameron could have been batting for British interests. Instead, he had put the Tory party's self-interest ahead of Britain's national interest. He could have built alliances over the preceding months, he could have insisted that a different deal was done rather than giving up on Thursday night. What was the alternative? He could have sought practical protections for our financial services industry rather than posturing. He could have insisted that crucial euro-area meetings affecting Britain should not take place without a British voice in the room. Instead, he has been too scared of his own backbenchers and too desperate to avoid a vote in parliament to stand up for Britain's national interests.
So preoccupied with stabilising the Tory party, Cameron has done nothing to help deliver the stability and growth in the eurozone that is so crucial to Britain's recovery. That should have meant support for the European Central Bank acting as a lender of last resort, and a recognition that ever greater collective austerity will never deliver the growth we need.
But neither of these steps were taken.
I fear that we will come to rue the fact that the summit was a political disaster and an economic failure for Britain and Europe. What does this mean for British politics? We know where the Tory party now stands. But it does not command a parliamentary majority.
Nick Clegg, the deputy prime minister and leader of the unashamedly pro-European Liberal Democrats, said before the summit that the key aim was to do "everything we can to avoid a great big split in the European Union" because that would be "bad for jobs and growth in this country".
Can Clegg really look his party – or the country – in the eye and say this has not now happened? It is time for him and Liberal Democrats to ask whether this is really what they came into politics for.
Cameron has not wielded a veto as he claims. He has simply lost.
This is a terrible outcome for British business, British jobs and for Britain.
By Ed Miliban, leader of the Labour party and MP for Doncaster North.