Právě že si takovou situaci nedokážu moc dobře představit.

Gerard Lyons, chief economist at Standard Chartered, says there have been several examples of monetary unions that have collapsed because they were not accompanied by fiscal union: "For monetary union to survive, it has to become a political union. If it doesn't there is likely to be some sort of implosion and a move towards a two-speed Europe."

Roubini agrees: "The eurozone could drift … with a strong centre and a weaker periphery, and eventually some countries might exit the monetary union."

Mats Persson, research director of the Open Europe thinktank, believes Greece should not have been allowed to join the euro in the first place, and that there comes a point during an extreme crisis when countries can see the desirability of having their own currencies, so that they can adjust through devaluation: "The question is whether Greece can ever compete as a middle-rank eurozone country without some proper structural reform, and whether that is possible without its own monetary policy."

France threatens to leave the euro. German savers hoard gold. The Bundesbank works on a plan B to restore the Deutsche Mark. It's fair to say even a $1 trillion bailout hasn't been enough to stop the rumour mill dogging the European single currency this week.

How much truth there is to these rumours we'll probably never know. The Elysée was predictably playing down reports of Nicolas Sarkozy's threat yesterday. A spike in gold prices to more than ¤1,000 an ounce can only be partly due to Germans buying gold coins, and if the Bundesbank does have a plan B, it won't be telling the blogosphere first.