Why Princess Diana's Famous Taj Mahal Photo Almost Didn't Happen

courtesy Anwar Hussein Princess Diana

Princess Diana "knew which way the story would go" when she sat solo in front of the Taj Mahal in 1992.

Royal photographer Anwar Hussein opened up to PEOPLE about taking the famous photo, one of 140 images featured in Princess Diana Exhibition: Accredited Access, in which Hussein reveals the stories behind his iconic photos.

Princess Diana and Prince Charles visited India in February 1992, the year they would later separate.

Historically, "the Taj Mahal exists as the eternal monument of a husband's love," Anwar says of the mausoleum built by the order of Mughal emperor Shah Jahan to honor his wife. "I photographed Charles there just before he got engaged. He said to us then, 'I'd like to bring my girlfriend or future wife here one day.' "

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The day of Princess Diana's visit, Prince Charles was at another meeting and Diana appeared for the outing alone.

"We didn't know if she would come. She kept us waiting for a long time," says Anwar, now 83. "It was really, really hot there. She looked sad, and she knew which way the story would go. She was very clever. There were other pictures taken that day on another bench when she seemed to be contemplating things."

Samir Hussein/Pool/WireImage Kate Middleton and Prince William

Anwar's sons Samir and Zak followed in their father's photographer footsteps. In fact, Zak snapped the photo of Prince William and Kate Middleton during their 2016 visit to India.

"It was around 122 degrees, and we were waiting in the sun for about five hours," Zak recalls. "The press officer said it was going to be up to [William and Kate] to decide if they'd sit in the same place at the last minute. But they sat at the bench. I was shooting it knowing in the back of my mind I was taking a historic picture. It was a once-in-a-lifetime opportunity."

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courtesy Anwar Hussein The new photo exhibit, "Princess Diana: Accredited Access," opens up Anwar Hussein’s remarkable archives to the public

He continues, "Dad is proud of the fact that I had photographed her son there in exactly the same situation. He's pleased with the results of it because I didn't mess it up. It means quite a lot to us as a family that we have two generations shooting two generations."

Princess Diana Exhibition: Accredited Access is currently open in Los Angeles and Chicago, with plans to come to New York City. For information and to reserve tickets, visit princessdianaexhibit.com. Use promo code PEOPLE15 to receive 15% off.