Wien says that the eurozone can be divided into those countries that run a trade surplus (such as France, Germany, the Netherlands, Finland and Luxembourg), and the deficit countries of Greece, Portugal, Spain and Italy.

But he points out that the deficits of Spain and Italy are relatively modest. “Spain and Italy have viable economies and they’re able to export products that people want to buy. So I think that Spain and Italy are salvageable. I’m not sure that that’s the case for Greece and Portugal.”

Wien says he agrees with comments made by Greece’s former prime minister, Lucas Papademos, that a Greek exit from the eurozone would be “catastrophic” for the country. The country, he says, will get little benefit from returning to a devalued drachma. "What are they going to compete on? Olive oil and tourism?”