The Royal Mail is launching trials of parcel deliveries and office openings on a Sunday.
Customers will be able to collect parcels at around 100 offices on a Sunday from this weekend, while parcel deliveries will be made within the M25 area.
Royal Mail said the move would make it easier for online shoppers not at home during the day to pick up parcels on a Sunday, with offices open for four hours from noon.
Nick Landon, managing director of Royal Mail Parcels, said: "We are continuing to be more customer-responsive and provide more options for people to receive items they have ordered online.
"I am delighted to pilot Sunday afternoon opening at around 100 of our delivery offices across the UK with the highest parcel volumes, and Sunday deliveries to addresses within the M25 motorway."
Dave Ward, deputy general secretary of the Communication Workers Union, said: "Royal Mail employees are keen to work with the company to improve services for customers. Delivering on Sunday is an important initiative and one of the ways in which Royal Mail, with the help of its workers, is modernising.
"We've negotiated that staff can opt to work on Sundays voluntarily and we've ensured they are properly compensated. We have worked hard to make sure that Royal Mail is committed to using full and part-time staff rather than agency workers."
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