'The Bank's roles and functions have evolved and changed over its three-hundred year history. Since its foundation, it has been the Government's banker and, since the late 18th century, it has been banker to the banking system more generally - the bankers' bank. As well as providing banking services to its customers, the Bank of England manages the UK's foreign exchange and gold reserves and the Government's stock register.'
(Source: Bank of England website http://www.bankofengland.co.uk)