David and Diana took a few pictures during their time collaborating on this series, but he kept this portrait in his personal archives, which is why it wasn't made public until now.
It was the Princess who chose David to photograph her, and she was the second royal he worked with. His first was Lord Snowdon, the husband of Princess Margaret, who was also a photographer.
According to Hello Magazine, the piece will be joined by iconic photos of the royal family while off-duty, which will traverse the generations of Queen Victoria to the present day.
A selection of photographs taken by the royal family will also make their debut at Kensington Palace, which will speak to the fondness royals have found for the camera despite finding themselves its eternal subject.
Naturally, the exhibition has included Lord Snowdon's pictures from his time as a Kensington Palace resident. He was one of Britain's most revered photographers that took many images of his royal-in-laws.
Considering Duchess Catherine is famously a keen photographer who has had her work featured in exhibitions and is known for taking her family portraits, royal fans may discover some unseen gems created by the Duchess at the gallery.
This article originally appeared on our sister site, Now To Love.