A royal photographer who travelled the world with Princess Diana shares his favorite photo of the royal on her 60th birthday

• Princess Diana's photographer Tim Rooke shared his favorite photo of the royal.
• The photo was taken by Rooke on Diana's 36th - and final - birthday.
• Thursday, July 1 marks what would have been her 60th birthday.

Shutterstock's Royal photographer Tim Rooke has paid tribute to Princess Diana on what would have been her 60th birthday by sharing his favorite photo of the royal.

Rooke became a royal photographer in 1990, and went on to photograph Diana at royal engagements across the world and in her home city of London.

Rooke told Insider that his favorite photo of the princess (above) shows her smiling at his camera as she arrived at the Tate Gallery in London in 1997.

"What Princess Diana used to do was always just turn and look before entering a building. She'd just glance at the photographers at the last second and it always produced the most striking of photos," Rooke said.

"I took a picture of her on her 36th birthday, which sadly was her last. She was at a reception at the Tate Gallery in London. Just before she went in she turned back and smiled, and it made an absolutely stunning picture," he added.

In a video of Diana arriving, taken by AP, photographers can be heard shouting over to the princess: "Happy birthday, ma'am."

Rooke said Diana was "the first royal who truly knew how to work the camera" and that she was "always a joy to work with."

"The younger royals are less likely to turn for the camera as they tend to talk to the person that's greeting them, but of course they're being polite," he added.

The event was also attended by Diana's brother, Earl Spencer.

"The last time I saw Diana was on July 1, her birthday in London, when typically she was not taking time to celebrate her special day with friends but was guest of honour at a special charity fundraising evening. She sparkled, of course," Earl Spencer said at her funeral in September that year, Hello! Magazine reports.

Prince Harry and Prince William are teaming up to mark Diana's 60th birthday on Thursday with the unveiling of a statue in her honor at Kensington Palace.

The statue, designed by Ian Rank-Broadley, will stand in the palace's Sunken Gardens.