I don’t think I have ever attended an international summit that delivered a perfect outcome. It is the nature of Summitry, the land of compromise.

It is also more likely that the more complicated the Summit structures, the less perfect the likelihood of the outcome. And they don’t come much more complicated than Copenhagen.

Even if you penetrate the apparent chaos on the outside, with thousands milling around feeling their importance is not being recognised, there are thousands more inside arguing over big points – like will we save the planet – and small points – like should that be a comma or a semi colon?

But as the negotiations reach a deadline, the power tends to shift from the many who have been involved in a long and tortuous process, to the few who have to seal the deal.

It is at moments like this that you feel the power of leadership, and the relative power of different players on the world stage. Hillary Clinton’s arrival clearly gave impetus to the process, in part because she and her people will have been insisting that things be put in better order by the time President Obama arrived. Gordon Brown is a man capable of haggling over single words and punctuation if he has to. But he will have known on arrival that was not where the needs of this particular Summit were, and clearly cut through a lot of the stuff that was holding up progress amid all the Point of Order mentality that can block a deal. Instead he used power and energy, and alliance with other like-minded leaders, to get things moving.

And of course Obama, both because he is US President and because he is Obama, will now add a whole load of impetus of his own.

It could still be that even the imperfect outcome which looks reasonably likely now will fall apart before the day is out. More likely is that there will be moments when it feels like that, moments when it looks like it is coming together, and then a version of it will.

Don’t be surprised to see tears and tantrums from those who have been toiling for months on this. People get very emotional at the climax of long negotiations. Don’t be surprised to see plenty of celebration. And then plenty of hard-headed analysis around the world as people try to work out what the deal will actually mean.

I heard someone yesterday saying angrily ‘why can’t they just sit down and agree? This is too important.’ Yes, but so are the issues being raised that prevent an agreement. So are the different perspectives held by different countries. So are the politics of different countries.

It’s like when people say ‘why can’t the UN sort it out?’ Because the UN is just a collection of the countries of the world, supported by a very odd bureaucracy.

I’ve been at plenty of Summits where the miracle has been any deal at all. Copenhagen looks to be following that pattern.