A three-day strike by some Bank of England support staff has begun, after talks at the conciliation service Acas ended without agreement.
Employees in the Unite trade union are disputing a below-inflation pay rise of 1%, which has been imposed.
About 20 union members, including cleaners, security and maintenance staff, are picketing the Bank's headquarters in the City of London.
Some are wearing facemasks of the Bank's governor, Mark Carney.
They have been joined by the shadow chancellor, John McDonnell.
Staff in the Bank's "parlours", which are meeting rooms on the ground floor of the Bank's building in Threadneedle Street, have also walked out.
It is the first time for more than 50 years that workers at the central bank have been on strike.
"The union balloted approximately 2% of the workforce," the Bank said, as only 150 staff work in the three affected departments.
"The Bank has plans in place so that all essential business will continue to operate as normal during this period.
"The Bank has been in talks with Unite up to and including today and remains ready to continue those talks at any time," it added.
The last time Bank of England staff went on strike was in the late 60s and involved printers at the Bank's printing plant in Debden, who were employed by the Bank of England at that time.
Unite said the dispute centred on the "derisory" pay settlement that the bank had imposed on staff without the union's agreement.
It was the second year running that staff had received a below inflation pay offer, it said.
Unite's London and Eastern regional secretary, Peter Kavanagh, said its members had "been left with no choice but to take industrial action".
"Mark Carney should come to the picket lines outside this iconic British bank today and explain why hardworking men and women deserve to face years of pay cuts."
"They are struggling to pay their bills and feed their families because the bank has unjustly imposed a below inflation or zero pay rise," he added.
Inflation was 2.6% last month, according to official figures.