sentences:  The ECB had "crossed the Rubicon" and was in an untenable position, struggling to carry out its conflicting roles as agent of monetary policy, banking regulator, and Troika enforcer.Noting that the bank already held over €1 trillion of bonds bought at artificially low or negative yields, so would face great losses when interest rates rise again, he warned.The reputational risk of such actions by a central bank would have been unthinkable in the past."