LONDON - Britain's Royal Mail announced on Tuesday it planned to issue two official stamps to commemorate the wedding of Prince William to Kate Middleton.

A set of commemorative stamps, to celebrate the wedding of Britain's Prince William and Kate Middleton, is seen in this photograph received in London on March 28, 2011. [Photo/Agencies]

The stamps will feature photographs taken by Mario Testino to mark the couple's engagement and will be available at post office branches from April 21, eight days before the ceremony.

"We are honoured to be celebrating this very special and historic occasion," said Stephen Agar of the Royal Mail.

"We believe that that this set of stamps will be very popular with people both in the UK and around the world."

The postal service said Queen Elizabeth gave the final approval for the issue of the stamps.

It is the third time Prince William has appeared on a Royal Mail stamp -- he featured on a sheet of stamps to celebrate Queen Elizabeth the Queen Mother's 100th birthday in 2000 and in 2003 became the first member of the royal family to have a set of stamps produced to celebrate their 21st birthday.

He is also the first of the queen's grandchildren to have their wedding commemorated on a set of stamps.

The commemorative stamp sheet consists of two first class stamps and two 1.10 pound stamps, which capture the couple in both formal and informal poses.

The formal image was taken in the Council Chamber of St James's Palace in London while the informal image shows the couple in the Palace's Cornwall room.