Catherine, Princess of Wales was forced to run barefoot in a parents' race on school sports day.
The 41-year-old royal - who has Prince George, ten, Princess Charlotte, eight, and Prince Louis, five, with Prince William - has revealed that she and her husband both became very competitive on school sports day.
During an appearance on 'The Good, The Bad and The Rugby' podcast, the princess said: "There are lots of schools that have banned parents' races because it has become far too competitive."
Asked if she would take part on sports day, she replied: "We have done!
"We were told categorically there was no parents' race. But then they called a last-minute parents' race, and me with the competitive side, both of us were like … we have to take part. So I had to do it in bare feet."
William, 41, has also admitted to being very competitive with the other parents.
The future monarch - who became the President of England's Football Association back in May 2006 - said: "I came second. I started off just running, joining in and looked round. I was quite far out in front and there was an Italian dad in front and I thought I've got to catch him."
The princess added: "And I ran in barefeet in the same race."
The princess is a big sports enthusiast and she actually loves to go swimming in cold water.
She shared: "I really, genuinely love all sports. Personally, I love swimming wherever I can.
"Cold swimming - the colder, the better. I absolutely love it. Slightly to the point where William's [saying], 'You're crazy' and it's dark and it's raining.
"I will go and seek out cold water. I love it."