What does veto mean for Cameron and UK?
David Cameron has wielded his veto and won plaudits from his Eurosceptic backbenchers.
Even his old sparring partner, the London Mayor Boris Johnson, says he has "played a blinder".
But his stance, which scuppered an EU-wide deal to prop up the euro could still have damaging consequences.
It is clear the prime minister was presented with proposals which he simply could not accept.
He feared that the plans on the table would undermine the City of London, which is still such an important part of the British economy.
Foreign Secretary William Hague, himself a staunch Eurosceptic, said this morning that it would have cost us control over our taxation and spending, thus endangering the policies that have spared us from a Greek-style crisis so far.
Conservative MPs are praising Mr Cameron for sticking to his word and refusing to sign a deal that would have meant a transfer of power from Westminster to Brussels.
The prime minister believes this means there will be no need for a referendum.
But there will be some in his party who believe that there has been such a substantial change in Britain's relationship with Europe, that there should be a referendum.
Others will urge their leader to seize this opportunity to wrest power back from the EU on matters such as the Working Time Directive, Social Chapter, agriculture and fisheries policies.
Given the undisguised irritation of key European leaders such as Nicolas Sarkozy, he is hardly likely to get a sympathetic response to such demands at the moment.
Club within a club
We are told that Mr Cameron discussed his stance with his Liberal Democrat Deputy Nick Clegg and the approach had the backing of his more pro-European coalition partners.
Many Liberal Democrats though will be concerned that Britain will end up sidelined in the key discussions on Europe's future.
There is clearly the risk, which Mr Cameron himself acknowledged, that those who have signed up to the deal will take important decisions without us.
Some of these could yet have repercussions for the UK. It is far from clear how we can wield power and influence in Europe outside a club that includes all the other major players.
There is a far more profound danger too.
For David Cameron and all the European leaders the key objective of this summit has been to put together an agreement which could provide a lasting solution to the problems of the eurozone.
The reaction on the markets so far is not reassuring, though they are waiting to see the details of the deal.
If the markets take the view that without proper treaty changes the deal is insufficient to underpin the economies of countries like Greece and Italy, then ultimately the summit will have failed.
The French president is already blaming his "British friends" for preventing a treaty change which involved all 27 EU countries.
If, after all this, the eurozone heads further into crisis, attitudes towards Mr Cameron could sour still further.
Chancellor George Osborne has already warned of the dire consequences for Britain if there is a disorderly breakup of the eurozone.
The real test of this summit will be what happens to the economies of all the countries of Europe.