Festive fun was the order of the day as Prince William showed his wife the work of Centrepoint – a homeless charity introduced to him by his mother.
First up for the royal couple was a cooking session at Camberwell Foyer, a shelter run by the organisation for youths aged 16-25.
With their sleeves rolled up and both in aprons, the duo made cookies topped with hundreds and thousands.
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On learning that it was 18-year-old Tasha Barbi's birthday, the Duchess of Cambridge got to work on a heart-shaped cookie, telling her: "It's your birthday cookie!"
Then, the Duke joined in a dance routine with some of the residents. Vanessa Boateng, also 18, put him through his paces – much to Kate's amusement.
"Dust off your shoulder twice," the teenager instructed William, referring to the hip-hop move she was demonstrating.
They also had a chat about the royal wedding. Asked by the Duke whether his suit had been "dapper", she replied: "Your swag was on point", street speak for he looked good.
Vanessa, who is training to become a nursery nurse, also disclosed that the VIP visitor talked about his hopes for a family.
"He said he was going to make his children come and I could discipline them" she revealed.
The future King has long been associated with the organisation, which was one of his mother Princess Diana's favourite causes.
Speaking about the charity, he once said: "I remember my mother taking myself and Harry to visit it when we were children.
"I was much younger, better looking and naïve then, but it helped to open my eyes to the world so many young London people face."
Diana was patron of the charity from 1992 to 1997.