Four generations of the British Royal Family are featured on a new stamp in honour of the Queen's 90th birthday.

Young Prince George is sporting a big smile as he stands on foam blocks and clutches his father's hand in his Royal Mail stamp debut.

Queen Elizabeth II, Prince Charles, Prince William, Duke of Cambridge, and Prince George of Cambridge were photographed last summer in the White Drawing Room at Buckingham Palace by Royal Mail photographer Ranald Mackechnie.   

The limited edition stamp is one of several stamps and souvenirs that are being released by Royal Mail to mark the Queen's birthday, which takes place Thursday.

The Queen was treated to a rendition of ‘Happy Birthday’ performed by the Royal Mail choir on Wednesday during a visit to the postal service’s offices.

The Royal Family has marked number of milestones with the release of a stamp, including the engagement of the Duke and Duchess of Cambridge.