First Greece, then Portugal, and then what? The project of European monetary union is entering the most dangerous phase in its 11-year history. Last week, eurozone governments started preparations, for the first time, to bail out one of their fellow members. Greece will probably require a bridging loan at some point. Portugal might too. But they are small countries. No matter what happens, it will not break the euro.

The clear and present danger to the eurozone is Spain. Daniel Gros of the Centre for European Policy Studies argued on these pages last week that Spain is in a better position than Greece because of its higher rate of gross national savings. But I believe that Spain is likely to squander that advantage. Spain, like Greece, has suffered from an extreme loss of competitiveness during a period in which it relied on a housing bubble to generate prosperity. While the Greek government is at least beginning to recognise the need for reform, perhaps too late, Spain's political establishment remains in denial.

So what if Spain gets into trouble? Will the eurozone falter, as Nouriel Roubini, professor of economics at New York University, predicted in an interview last week? The question is unanswerable. I find it more constructive to ask what the eurozone will need to do to survive the strains ahead. Three measures are, in my view, essential for survival; a further three almost so.