In his masterful account of the Great Depression in the US, the historian David Kennedy recounts how disaster spread through the banking system.

“As the beleaguered banks desperately sought cash by throwing their bond and real estate portfolios onto the market ... they further drove down the value of assets in otherwise sound institutions, putting the entire banking system at peril,” he wrote. “This liquidity crisis threatened to become a roaring tornado that would rip the financial heart out of the economy.”