By Mark Mardell
BBC Europe editor
Straight after the signing, Germany's leader nearly got left behind.
As the other 26 leaders waited on the bus that was to take them to the Brandenburg gate, Mrs Merkel had to push her way through the crowd, waving slightly anxiously, trying to catch up.
But this in no way works as a metaphor. Politically speaking Mrs Merkel is behind the wheel, driving at breakneck speed. The Germans want a new treaty to renew the political shape of Europe and "renew its political basis".
She warned it would be a "historic failure" if the process was not brought to a successful conclusion. She said that those who hoped there would be a constitutional treaty by now "will be disappointed".
Disagreement to overcome
Perhaps that was intended as no more than a statement of fact but it also points towards the one concession that has been made in private by fans of the constitution: the name itself will be dropped.
Mrs Merkel said that by June there should be a roadmap on the way forward. German diplomats have told me that to meet the deadline of getting functioning rules in place by 2009 there has to be an agreement by the beginning of next year at the very latest. That means a lot of work, and a lot of disagreement to overcome.
Many expect the guts of the constitution to be the basis of any new agreement. In his speech, the Italian Prime Minister said the leaders of 27 countries had backed it before the French and Dutch voted it down and provoked what he called "a period of mourning" so it should form "a very solid basis" for the future.
Tony Blair later said that the matter should be resolved "as quickly as possible", while not forgetting those No votes. Curiously, he did not answer my direct question if the British people would be allowed to vote on the result.
No more members?
What of the declaration itself? It will at least be a useful snapshot for future historians of the European Union's obsession and concerns in 2007.
It declares that the rights of individuals are paramount, and the diverse traditions and cultures of the member states enrich the European Union and should be preserved. It praises the euro and the common market for making the EU strong, and says the European model combines economic success with social responsibility.
It says that there are many goals which the EU countries can only achieve together and specifically mentions fighting climate change, organised crime, illegal immigration and racism.
There is one glaring omission. The most obvious way in which the EU has changed since the treaty of Rome is that then there were six countries, and now there are 27. But the declaration that the "unnatural division of Europe is now consigned to the past" and that the dream of the "unification of Europe" has become a reality make it sound very much like a completed task, not a work in progress.
In fact, apart from a vague reference to "openness" there is no mention of anyone else joining. Indeed, none of the official candidates for membership, like Turkey or Croatia, were invited. This is a row that has been ducked, but will have to be had.
Oblique language
It's also true that one of the European Union's stock phrases, "ever closer union," does not make an appearance. Instead, there is a reference to the EU thriving "on the will of its members states to consolidate the Union's internal development".
Angela Merkel later suggested that there was wide agreement that energy and home affairs should become areas where the EU can make laws.
The Germans have on the whole achieved their aim of writing an accessible and easy to understand document that won't cause offence in the governments of the member countries.
But to deal with that tricky issue of what happens to the constitution, the Germans had to use more oblique language.
While they avoid the word "constitution" itself, the declaration says: "We are united in our aim of placing the European Union on a renewed common basis" by 2009.
This is quick. Diplomats say to achieve the 2009 deadline there would have to be agreement at a big summit by next January at the latest.
Given that the real work can't start until the French choose a new president at the beginning of May, this means the wrangling has to take place in just eight months, or seven if you take out the August break. The Poles have come straight out and said this is unrealistic.
Eurosceptic newspapers
It will be difficult to find agreement between the maximalists, who really want to keep the old constitution and grudgingly accept it will have to be labelled a mere treaty, and the minimalists, like Tony Blair, who want something modest enough not to trigger demands for a referendum.
The question in Brussels is "what's the threshold?" in other words: what does the British Government see as a step too far, that would need a popular vote.
The real answer is "what the market will bear". How tough Mr Blair is, will depend largely on how tough David Cameron is, and how noisy the Eurosceptic newspapers are.
Fifty years on, the European Union is still that curious mixture of grand projects and statements and complex arguments about the rule book.
But it boils down to the question whether the EU is enough of a success to be given the new ways of working that its fans say will make it more efficient, and capable of greater things still.
