Postal workers in London began a three-day strike over jobs and pay today which was expected to cause major disruption to deliveries.
Delivery staff walked out today, distribution workers strike tomorrow and mail centre staff on Friday.
"Postal workers cannot continue with the levels of cuts on hours, jobs and wages by aggressive management which we are currently experiencing," said Martin Walsh, the Communication Workers' Union London representative, in a statement.
But Royal Mail countered: "It is nothing more than an attempt, backed up by strike action, to halt the modernisation process which is crucial to the company's future survival."
It said it has contingency plans in place, which should keep the inconvenience caused to a minimum.
Royal Mail managers from across the country will be working in London through the strike period to keep as many services running as possible.
More information is on its website www.royalmail.com/serviceupdateReuse content