The lesson from this European Union summit will be talked of in management seminars for years to come.
It will echo through the corridors and be whispered in the cafes. People will wonder why it was allowed to happen.
Differences over voting rights in the future EU could not be overcome
It is a quite simple lesson. If somebody already has an agreement in his pocket, do not expect him to accept something less.
That is what happened to Poland. It got a good deal on voting rights three years ago in Nice. Yet this year it was asked to give them up.
And this in the knowledge that the Nice arrangements would come into effect anyway if it said no.
Poland did say no.
The failure shows once again that the construction of Europe is not like the construction of the United States.
Where the young US strode forth to found a new nation, Europe is staggering along trying to accommodate all its nations.
They did nearly get there. But voting rights was the rock on which the ship, on this voyage, ran aground.
There will now have to be a pause while the ship is salvaged.
Schroeder warned of 'a twin-track Europe' forming over the deadlock
The Irish presidency takes on the task for the next six months. It will consult and question and no doubt will come back and report at the next EU summit in March.
There is no absolute hurry.
The 10 new members will join in the spring and the Nice plan - the default setting - will be put into effect.
Poland's decision was criticised by some.
John Palmer, Political Director of the European Policy Centre in Brussels said that member states got influence by "facilitating not stopping decisions. Britain found that out. The Irish and Finns always knew it. The Poles have to learn it."
He predicted that France and Germany would now try to move ahead with greater integration especially in home and justice affairs, raising another issue on which there would be a two-speed Europe.
There already is on defence and the euro.
He also felt that the Poles and Spaniards might have different governments by the end of next year when an agreement on voting might be tackled again.
"The failure in Brussels is not a disaster," he commented.
"It would have been a disaster to allow a watered down treaty which perpetuated the worst features of the Nice treaty."
What was striking after the meeting was that everyone was quite calm.
The Italian Prime Minister Silvio Berlusconi, chairman of the meeting, said that 82 of the 90 or so points of disagreement had been resolved.
"It was a useful job. It has not been a waste of time," he declared.
The British Prime Minister Tony Blair, for once not at the heart of the argument, agreed.
Poland's Kwasniewski: Unhappy over voting rights
"To look at this in apocalyptic terms is misguided," he said.
Mr Blair announced that the British "red lines" had been secured. These were demands that there be unanimity in taxation, criminal justice, foreign policy, social security and defence.
He went further.
There had been an agreement on defence allowing for an EU planning cell to be set up, but not in competition with Nato.
And so it is onto the Irish presidency on 1 January and then, if necessary after that, to the Dutch on 1 July.