The Duchess of Cambridge has attended official royal events with her in-law on many occasions.
When performing her royal duties with Prince Charles and Prince William, body language expert Judi James explained she has a vital role.
She explained Prince Charles will often appear happy when with his daughter-in-law.
“Kate’s role in Prince Charles’s life appears to be that of a catalyst rather than a friend or kindred spirit,” Judi told Express.co.uk.
“There are rarely if ever any signals of the kind of easy-going, spontaneous warmth he shares with his niece Zara.
“But the secret reason why he so often looks happy and fun-loving in Kate’s company might be more to do with the fact that she forms an integral buffer or air-bag role in the relationship triangle that includes his son William.”
The expert claimed Kate and Prince Charles may not have the closest relationship.
Judi continued: “There’s nothing to suggest a meeting of minds between Charles and Kate and when they are seen walking together Charles’s body language suggests he might be at a bit of a loss in terms of easy-going conversation.
“While the two men point and laugh open-mouthed to suggest there’s some kind of banter going on between them, Kate’s polite attention to Charles and her appreciative smiles as he chuckles suggests she might have mended a few bridges between them over the years.”
Prince William and Prince Charles are both also senior working members of the Royal Family.
Prince Charles is first in line to the British throne and it is thought he will take over from Queen Elizabeth II in the future.
Never miss a royal update again by signing up to the Daily Express Royal Family newsletter
How did Kate Middleton become a royal?
Kate Middleton, or Catherine, Duchess of Cambridge, was born on 9 January 1982 at the Royal Berkshire Hospital, Reading, England.
She was born to Michael and Carole Middleton, a former flight dispatcher and air hostess. The couple founded a party supplies company, Party Pieces, in 1987 – now estimated to be worth £30 million.
Kate has a younger sister Pippa Matthews and a younger brother James Middleton.
Kate and her family moved to Amman, Jordan, in 1984, where the future Duchess was educated at an English-speaking nursery school.
After moving back to Berkshire the family sent Kate to private school, St Andrews School. She went on to briefly study at Downe House before moving onto Marlborough College where she boarded.
For university the young Kate attended the University of St Andrews in Fife, Scotland. Here she was awarded an undergraduate MA (2:1 Hons) in history of art.
Relationship with Prince William
Kate met Prince William when they were both studying at St Andrews, and both living in St Salvator’s Hall. Famously, William reportedly took a fancy to Kate after she wore a see-through dress during a fashion show.
In 2003 the couple began dating and lived together during their second year of university.
The couple split in April 2007, however, in October they were back together.
Prince William proposed to Kate Middleton with his late mother Princess Diana’s engagement ring in October 2010. The couple were holidaying in Kenya at the time.
On 29 April 2011 they married at Westminster Abbey with a whopping 26 million watching the event live.
Kate wore an Alexander McQueen dress worth a reported £250,000 on the big day.
Kate assumed the title “Her Royal Highness The Duchess of Cambridge” and also became the Duchess of Cambridge on the day.