Kate Middleton isn’t one to break the royal rules.

During a surprise appearance at the RHS Chelsea Flower Show in London, U.K. on Monday — where she joined school kids for a picnic — Kate politely declined to sign autographs.

The children must have asked her to sign something, as Kate was overheard saying: “I can’t write my name… but I can draw,” according to People.

She’d been identifying bugs and beetles with students from St. Mary’s Church of England Primary School in Islington and Glenbrook Primary School in Brixton in the Royal Entomological Society garden at the time.

According to a previous Daily Express article, the reason the royals can’t sign autographs is because they run the risk of the signature being forged.

The Princess of Wales joined 100 kids from 10 different elementary schools for the inaugural Children’s Picnic.

READ MORE: Kate Middleton Looks Pretty In Pink As She Surprises School Kids With A Picnic At Chelsea Flower Show

She drew a flower for one 7-year-old girl called Ruby, as well as a tree for one of the other girls, and a pond surrounded by plants for a different pupil.

When questioned further on why she couldn’t sign her name on their sketches, Kate responded patiently, “My name’s Catherine. I’m not allowed to write my signature, it’s just one of those rules.”

During the surprise visit, Kate also spoke about her youngest child — 5-year-old Prince Louis — growing broad beans at school.

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“Louis is growing broad beans at school. You put them in a cup and you can see the roots growing. They get big quickly like sunflowers,” the mother-of-three explained.

She was also asked by the curious kids what being a member of the royals was like.

“You have to work hard, but you know the best thing about it is meeting kiddies like you,” Kate shared.

She then said of what the royal family does, “They help support all the different people in the country, showcase all the amazing work being done and look after everyone.”

Kate said when quizzed on whether she made the law, “The Prime Minister makes the laws.”