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Yet, the very next day, the palace requested that the photo not be published.

It wasn’t because the image was inappropriate, nor because Bowie appeared in it — it was about who else was with Diana.

The princess arrived at the concert accompanied by Major James Hewitt. At the time, there were rumors—later confirmed—about an affair between them, and the palace wanted to avoid fueling gossip. Hewitt kept a low profile, staying clear of the cameras. “No one knew who he was, so I had no reason to photograph him, and their relationship hadn’t become public yet,” O’Regan explained.

Because of this, he chose not to publish the photo and still supports that decision.

In her biography, Diana later mentioned that she faced criticism for her outfit that night. She’d worn leather pants, which didn’t sit well with the royal family.

Diana defended her choice, saying she wanted to appear the same age as the crowd she was with.

Almost 40 years on, the photo has finally been made public in a new David Bowie biography, featuring extensive material from photographer Denis O’Regan — including that once-hidden moment.

While the image no longer poses a risk to the royal family’s reputation, it highlights just how much effort went into controlling Princess Diana’s public image behind the scenes.