London: On the eve of Queen Elizabeth's 90th birthday, Royal Mail yesterday issued a set of 10 special stamps to mark the occasion, featuring four generations of UK monarchy with the Queen, Prince Charles, Prince William and Prince George.

The group family photograph taken last year appears as a stamp sheet, with perforations positioned to create a first class stamp for each of the four royals.

A handout image released in London on April 20, 2016, shows a Royal Mail postage stamp sheet that has been issued to mark the 90th birthday of Britain's Queen Elizabeth II on April 21, 2016. Pic/AFP

In behind the scenes images released today, the two-year-old Prince George, the youngest royal and third in line to throne, is seen balancing on four high density foam blocks stacked together and secured by tape to be made tall enough for the picture.

Prince George posed for a cheeky grin for his very first postage stamp alongside his father, his grandfather and the great-grandmother.

"It's great just to be asked to photograph a stamp, never mind four generations of the royal family. When I was asked about I was ecstatic but I had to keep schtum (quiet) for 18 months," Photographer Ranald Mackechnie said.

"It was an amazingly relaxing and light-hearted sitting. They were comfortable with one another and behaved like any family with their conversation and jokes. It was much more relaxed than when I've tried to take pictures with my family.

"The joy and energy coming out of George was fantastic. It lifted the whole shot and lifted the afternoon. He was on top form. He was quite fascinated by the lights. He took it all in his stride," said Mackechnie.