It is unrealistic to expect that financial regulators will be able to prevent all financial disturbances. The Bank, therefore, needs to be able to respond to disturbances when they happen. The main way in which it would do this is through the use of its balance sheet to provide liquidity to the financial system.
The Bank’s preference would be to do this through its usual daily operations in the cash market, providing liquidity to the market as a whole, rather than to individual institutions.