Few people know the euro like Klaus Regling. As a senior official in the ­German Finance Ministry during the 1990s, Regling helped lay the groundwork for European economic and monetary union. Then, after a stint as managing director at hedge fund firm Moore Capital Management in London, he headed the Brussels directorate that oversees the single currency, from 2001 to 2008 leaving just before the financial crisis that would wreak havoc on the euro area.

Last month Regling, 62, took charge of the European ­Stability Mechanism, a new bailout fund with capital of €700 billion ($905 billion) and lending capacity of €500 billion that European Union leaders see as a fire wall to contain the blocs debt crisis. If Spain requests EU assistance soon, as most analysts expect, the ESM would be able to buy the kingdom's bond issues, while the European Central Bank could purchase short-term Spanish debt on the secondary market. Regling discussed the European debt crisis with Institutional Investor International Editor Tom Buerkle during the International Monetary Fund's annual meeting in Tokyo last month.

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