EXCLUSIVE: Greece debt crisis may break the Eurozone

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Early flight home: Greece's exit from the Eurozone could lead to the departure of other PIGS countries

The 11-year-old European currency union is facing its most serious threat as several countries across southern Europe – notably Greece – are at risk of failing to meet interest payments on their outstanding debt.

All have debt-to-GDP ratios far above the 60% ceiling of what is reckoned to be manageable, as well as yawning fiscal deficits.

Yet the inherent constraints of being a member of a single-currency club mean these countries cannot adopt the usual emergency measures – inflation or currency