Which British bank failure helped trigger the 1866 financial panic known as Black Friday?

The failure of Overend, Gurney and Company helped trigger the 1866 financial panic known as Black Friday.

Overend, Gurney and Company was a major London discount house. It had moved beyond traditional bill discounting into riskier lending and investments, including railway-related ventures. When confidence weakened, the firm could not meet demands for cash and suspended payment on May 10, 1866.

The failure caused a run on banks and discount houses, disrupting credit markets and forcing the Bank of England to act as lender of last resort. The Bank obtained authorization to suspend the Bank Charter Act's restrictions, allowing it to expand note issue beyond the usual limit and calm the crisis.

The event is called Black Friday in British financial history, but that name is not unique. It is also used for the 1869 U.S. gold panic and, in other contexts, for major shopping days. Overend, Gurney's failure is the specific landmark associated with Britain's 1866 panic.