A photo showing Princess Diana and rock icon David Bowie smiling together at a London concert appeared to have been kept hidden for decades.

But why has the royal family kept it under wraps for so long?

Keep reading to learn more.

It happened in 1987. Princess Diana, then 25, was at a charity concert at Wembley Stadium, where David Bowie was set to perform that night.

The promoter Harvey Goldsmith organized the photo session, and Denis O’Regan, a photographer who had previously worked with Bowie, was invited to capture the moment.

O’Regan shared with the Daily Mail that Diana was offered the chance to take a photo with Bowie and wondered if he would agree.

Bowie said yes, and the picture was snapped.

Yet, the very next day, the palace requested that the photo not be published.