The Princess of Wales nearly always looks like the picture of poise and professionalism on royal engagements.
But she candidly admitted that there is one party of royal life she's "still working out" and confessed it was not her "natural thing".
Kate made the rare admission when she joined a Dame Kelly Holmes Trust event in Bath and took on the double Olympic champion at a game of bean-bag noughts and crosses – but came out second best.
When the Princess sat down for a private chat with a group of schoolgirls supported by the charity at St Katherine's School in Bristol, she opened up the floor to questions about herself after listening to their experiences about home and school life.
Afterwards, double Olympic champion Dame Kelly said when the schoolgirls quizzed Kate about being a "royal", the Princess said it was something "she had to learn".
Speaking for herself, Dame Kelly said: "A struggle to kind of know that you can be accepted and fit in, and still learning every day."
The double Olympic champion said public speaking was not a "natural thing" to many people and, commenting on Kate, added, "she said she's still working that out".
It came after Kate also admitted becoming a member of the royal family was something she never expected – but then she met and "fell in love" with William.
Asked if she wanted to be a "royal" by a pupil, the Princess replied it was something she had not expected but she "fell in love" with Prince William.
Commenting afterwards about the pupils' chat with the princess, Dame Kelly said she posed a question about Kate's three children asking if she saw different "traits" in them, and the royal replied, "Oh yes, definitely".
Dame Kelly said about the Princess, whose visit marked Mental Health Awareness Week: "She humanised everything to say not everyone's perfect. Doesn't matter what you've got, or what you're perceived to have, as an individual you’re still going to have those insecurities."
She founded her national youth development organisation on the belief that every young person needs a champion.
It pairs world-class athletes with youngsters who may have lack confidence or have other issues, so the sportsmen or women can pass on their winning mindset and help the children develop the skills and confidence they need to succeed in life.
The eight pupils from St Katherine's School in Bristol were taking part in the On Track To Achieve programme, delivered by their athlete mentor, Paralympic gold medallist Liz Johnson.
When she first arrived, Kate, who is known for her competitive streak, took part in an outdoor game to relax everyone, joining some of the eight students aged 11-14 being supported by the trust, while the former sports star joined the remaining pupils on an opposing team.
In bright summer sunshine, each team member ran forward and threw a bean bag onto a grid on the ground.
Kate's team did their best but Dame Kelly's players twice won and, after their first victory, the track and field star held her arms aloft and admitted she was "slightly competitive", and the princess joked "You would never have guessed".
After the visit, Dame Kelly said she hoped it would lead to her trust working with the princess's Royal Foundation, which she said could provide opportunities and resources for her organisation which was started 15 years ago.
She added: "I wanted to work with young people, I wanted to make a difference and still believe that one person can make a difference. And I just realised that athletes have the ability to draw out those real-life lessons you get in sport.
"It isn't about sport and being an Olympic champion, but it is about what sport can bring to you."
