Prince William proved there is still laughter at home amid wife Princess Kate Middleton‘s cancer battle. He shared their daughter Princess Charlotte‘s “favorite joke at the moment” with a group of students during a royal visit on Thursday, April 25.

William, 41, made his first solo trip outside of London to meet with kids from the St. Michael’s Church of England High School in Birmingham, England, to discuss mental health. He was asked to produce a “dad joke,” but opted to share a knock-knock joke from his little girl, as it would help the kids “interact” with him.

The future monarch started the knock-knock with the words, “interrupting cow.” Before the students were able to ask, “Interrupting cow who?” William let out a loud, “Moo!” to a round of laughter.

“That’s one I hear a lot at home,” William said of how Charlotte, 8, loves the humor, adding that there might be more spicy jokes between him and Kate, 42. “That’s the only one I can think of that’s clean and broadcastable,” he quipped.

Prince William Shares Princess Charlotte's Favorite Joke
Max Mumby/Indigo/Getty Images

The heir to the British throne made his first solo public royal appearance since Kate’s cancer diagnosis on April 18, however, he remained close to the family’s home at Windsor’s Adelaide Cottage.

William toured a surplus food distribution charity called Surplus to Supper in Surrey, southwest of London, then traveled to a youth center in ​West London where the goods were delivered.

At the first location, one of the workers gave the prince get-well cards for both Kate and King Charles III, who is also battling cancer. He told the volunteer, “You’re very kind. Thank you very much.” She asked the royal to “look after” his ailing wife, as William sweetly promised, “I will.”

The Princess of Wales announced in a video on March 22 that after undergoing major abdominal surgery in January that left her out of the public eye during 2024, “tests after the operation found cancer had been present.”

“My medical team therefore advised that I should undergo a course of preventive chemotherapy and I am now in the early stages of that treatment,” she told viewers while sitting alone on a bench in her backyard.

Kate said the diagnosis came as a “huge shock” her and William and that “it has taken us time to explain everything” to their children – Prince George, Charlotte and Prince Louis – “in a way that is appropriate for them and to reassure them that I’m going to be OK.”

The family then headed to their country home, Anmer Hall, in Norfolk, England, during their children’s spring break from school. William was spotted at a local pub with his mother-in-law, Carole Middleton, while he took Prince George, 10, to an Aston Villa soccer match on April 11 in Birmingham, England.

The ​monarch-in-waiting returned to public appearances upon the family’s return to Windsor, when the kids headed back to classes on April 17.