Charles Spencer shares never-before-seen photo of Princess Diana on her 60th birthday

Charles Spencer shared a rare photo of a teenage Princess Diana to celebrate what would have been her 60th birthday on Thursday, July 1.

The 57-year old shared the black-and-white picture of his sister on the social media pages of Althorp House. It shows the late princess in a white turtleneck sweater, dark-coloured skirt with white trim, and white knee socks with her hair tied into pigtails.

"Today is the 60th Birthday of Diana, Princess of Wales. 1 July 1961 was an exceptionally hot English summer's day, Diana's parents always remembered," the 9th Earl of Spencer captioned the photo posted on Twitter and Instagram.

"She was born in Park House, on the Queen's Sandringham Estate in Norfolk," he continued as he pointed out that Park House is seen in the background of the family photograph, which he shared was taken by their father, the 8th Earl of Spencer.

Aside from sharing the throwback photo, the "White Ship" author also attended the unveiling of Princess Diana's statue in the redesigned Sunken Garden at Kensington Palace. He and his sisters Sarah and Jane were invited to the private event.

Brothers Prince Harry and Prince William entered the garden together smiling and laughing. They then stood on either side of the statue covered in green cloth to reveal it to the public.

Aside from the 9th Earl of Spencer and his sisters, the statue committee, Ian Rank-Broadley, Pip Morrison, and Chair of Historic Royal Palaces, Rupert Gavin, were also at the event, according to US Weekly. Other members of the royal family were not present. These include Kate Middleton, Queen Elizabeth II, Prince Charles, who is said to be in Scotland, and Meghan Markle, who is back home in California with her two children with Prince Harry.

Meanwhile, fans of the late Princess of Wales celebrated her 60th birthday with flowers and photos as they gathered outside the gates of Kensington Palace.

This is not the first time that Charles Spencer shared throwback photos of Princess Diana. In November last year, he also posted a picture of the two of them as children. It showed him wearing a blue collared shirt and matching shorts standing beside the young Princess of Wales, who is in a pink striped dress.