When the conversation turns to actively managed currencies, some financial theory purists contend they are a zero sum asset – noting that for every winning trade there is an equal and opposite loser. Other scholars call currencies a zero return asset, on the grounds that currencies have no embedded interest or dividends, and thus no intrinsic value or expected return.

“On top of that, the foreign exchange markets are incredibly efficient, so there should be no way that a manager can make an excess return,” observes Dori Levanoni, a partner at First Quadrant, a manager of $14bn (£8.9bn, €10.9bn) of currency strategies based in Pasadena, California. But in the most difficult year for the financial markets in many years, active currency managers as a group are reporting positive returns over 2 per cent in 2008, and many have generated Libor plus 10 per cent.