Roman Olearchyk writes: A corruption investigation and a high-level resignation are threatening to plunge Ukraine's central bank into turmoil, undermining Kiev's ability to stabilise its currency and pull out of a deep recession. Oleksandr Savchenko, deputy head of Ukraine's National Bank, the central bank, resigned yesterday, accusing colleagues of pursuing failed monetary policies and of co-conspiring in "currency speculation" deals that broke trust in Ukraine's hryvnia, causing it to plunge.
