Kate Middleton’s Cancer Announcement Video ‘Took a Lot’ as She’s ‘Inherently Shy’ (Exclusive)

The Princess of Wales was “sincere, dignified, poised” as she shared her health update with the world, says royal biographer Sally Bedell Smith.

LONDON, ENGLAND – NOVEMBER 18: HM Queen Elizabeth II and HRH Prince Philip, Duke of Edinburgh are joined at Clarence House by their immediate family, HRH The Prince of Wales (L), HRH Princess Anne, The Princess Royal (above C) , HRH The Duke of York (TopL) and HRH The Earl of Wessex (TopR) on the occasion of a dinner hosted by HRH Prince Charles, Prince of Wales and HRH Camilla, Duchess of Cornwall to celebrate the forthcoming Diamond Wedding Anniversary of the Queen and The Duke, on Sunday November 18, 2007 in London, England. (Photo by Tim Graham/Getty Images)

Kate Middleton overcame her “inherently shy” nature to deliver some difficult news.

In a video released on March 22, the Princess of Wales told the world that she was undergoing treatment for cancer discovered in post-operative tests following her January abdominal surgery.

Royal biographer Sally Bedell Smith tells PEOPLE that Princess Kate, 42, was “sincere, dignified, poised, and she was forthright” in her delivery, but the announcement likely wasn’t easy.

“She is inherently shy, and for her to do that took a lot,” Bedell Smith adds.

While the health update was extremely personal, Princess Kate acknowledged the many others who are also facing cancer, echoing something the late Queen Elizabeth may have done.

“When she ended with ‘You are not alone,’ it rang a bell with something that Queen Elizabeth would have said,” Bedell Smith explains. “It was very similar to what Queen Elizabeth said during COVID when she said, ‘We are all in this together.’ ”

“She was mindful there are very few people who read about that or watched that who doesn’t know someone who has cancer. She was mindful of that,” the journalist and biographer continues. “It was a way of reassuring people not only about her condition but helping them have courage.”

There was not a trace of self-pity. She projected honesty,” Bedell Smith says. “It was the right balance.”

In addition to writing “every word” of the announcement herself, the Princess of Wales also opted to appear on camera alone, without even her husband, Prince William, by her side.

“It is a message from the princess about her health, and she wanted to personally deliver the message on her own,” a palace source tells PEOPLE, adding that the Prince of Wales, 41, has been “supporting her throughout” behind the scenes.

“William is extremely proud of his wife for the courage and strength she has shown not just this week but since her surgery in January,” the source says. “Now more than ever, he’s focused on ensuring his wife has the privacy she needs to fully recover and that his children are shielded from the understandable interest in the news that has been shared.”