Prince William and Kate Middleton

Britain's Royal Mail will issue a new set of stamps to commemorate Prince William and Kate Middleton's upcoming wedding.

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The stamps will feature the couple's official engagement portraits, which were taken by fashion and celebrity photographer Mario Testino.

"We are honored to be celebrating this very special and historic occasion," Stephen Agar of the Royal Mail said. "We believe that that this set of stamps will be very popular with people both in the U.K. and around the world."

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The stamps have been approved by William and will be released eight days before the wedding on April 21 — Queen Elizabeth II's 85th birthday. They can be ordered starting April 7.

This will be the third time William has been featured on a stamp. He was featured on a sheet in 2000 to celebrate the Queen Mother's 100th birthday and in 2003 for his 21st birthday.