Cameron's EU headache
"We have not found a golden ticket".
That is the answer coming from Downing Street to those sceptics who claim that the prime minister has a once-in-a-lifetime opportunity to reshape Britain's relationship with Europe.
Some argue - as the Conservative former Europe minister David Davis did today - that the euro' s crisis is the UK's opportunity.
Their case is that the eurozone needs David Cameron and Parliament to agree to any new treaty designed to tighten the rules which govern the deficits, the debts and, by implication, the tax and spending policies of the members of the eurozone (that's what the dreadful phrase "fiscal union" really means).
Thus, he can extract a very high price for simply not vetoing the whole idea.
Not so, reply the mandarins of Whitehall.
The 17 members of the eurozone could form their own new club with their own new rules and, indeed, they have already done so.
The ESM or European Stability Mechanism - the name of the euro's bail-out fund - was created in just this way.
Thus, they argue, the PM's bargaining power is limited as the eurozone countries could simply bypass him.
What he can and would do, we're told, is fight to stop the officials and the resources of the EU from being used to help this new club which might, incidentally, have more than 17 members if those countries hoping one day to join the euro sign up as well.
Were this to happen the dispute about what European Commission officials could and could not do and what the new club could and could not discuss could end up in court.
So David Cameron's aim is to assist a deal of the 27 at a price much lower than many in his party want.
He will feel reassured by the support of his former boss and the Tories' former leader Michael Howard who today echoed the PM's view that what really matters for Britain is bringing an end to the euro crisis.
PS: James Landale has produced a valuable ready reckoner to measure the success or failure of this summit from David Cameron's perspective. Clearly the prime minister's critics would measure triumph or disaster in very different ways.