Deutsche Bank shares tumbled to a 30-year low on June 30 after the International Monetary Fund and the US Federal Reserve delivered the German lender a double whammy, saying it posed a significant risk to financial stability.

The IMF said Deutsche Bank was the riskiest financial institution in the world as a potential source of external shocks to the financial system. That came right after a US unit of Deutsche Bank was one of just two banks to fail the Federal Reserve's "stress test", an exercise measuring how 33 banks would fare in the event of another financial crisis.