The support of her "rock," also known as Sophie, Duchess of Edinburgh, allowed the Princess of Wales to make it through her most recent public engagement without complications.

As they joined the royal family for the Remembrance Day service in London on November 10, the couple was so devoted to one another that they were like glue and stuck together, New Idea Magazine reported. Amid her successful cancer treatment, Princess Kate, who is 42 years old, made a rare appearance in public.

A royal biographer named Claudia Joseph stated in an interview with The Sun that the "unbreakable bond" between Duchess Sophie, who is 59 years old, and Princess Kate was readily apparent when they conversed on the balcony of the Cenotaph before the event.

After some time had passed, as they were turning to leave the solemn ceremony, Duchess Sophie placed a supportive hand on the back of her niece-in-law.

Although the royal wives have always had a close relationship, Claudia believes that the most recent contact demonstrates that their friendship has grown stronger after Princess Kate was diagnosed with cancer.

"I'm sure Sophie has been a tower of strength for Kate," Claudia added.

At Queen Elizabeth II's suggestion, the two first became close. When fellow commoner Princess Kate joined the royal family in a more official position following her engagement to the now-Prince of Wales in 2010, the late queen asked Duchess Sophie to function as an unofficial mentor.

Claudia stated that since then, "they have developed a mutual respect," Another aspect of their connection that they appreciate is that it also has a lighter side.

There is just a fifteen-minute distance between the residences of the families of Princess Kate and Duchess Sophie. Princess Kate, Prince William, and their three children reside at Adelaide Cottage in Windsor, while Duchess Sophie and her husband, the Duke of Edinburgh, reside nearby at Bagshot Park, as per Town and Country Magazine.

"They're both really at home in the countryside and love bringing up their children with lots of fresh air and going on dog walks," Claudia revealed.

Numerous occasions throughout the years have seen them laughing and joking together at events such as Trooping the Colour and Royal Ascot. Additionally, they have a mutual appreciation for fashion.

"Sophie has become a true confidant and sounding board for Kate," Claudia added. "They are incredibly close."

Business Times has reached out to Princess Kate and Duchess Sophie for comments.