Users can design "Smilers" stamps on the Royal Mail website, where they can personalise a christening card with the picture of a newborn, for example, or create a design for weddings and birthdays.
Sean Tweddell, digital strategy and planning director at Royal Mail, said: "UK consumers increasingly want personalised products and services and Smilers stamps fit right in with that demand. Proximity London's excellent creative ability helped us create a website that makes our customers' lives easier."
Prices of the stamps, which include first class delivery, begin at £14.95 for a sheet of 20. The stamps are available to design at the Royal Mail website.
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