The royal spoke with health care professionals and met patients who were introduced to art through a trailblazing project at the Barts Health NHS Trust.
WATCH: Kate Middleton teases fans on the day of her book launch
At one point, the Duchess was left amused as picked up a book by Chris Haughton called "Oh No, George!" She said: "That's very appropriate."
The book, for ages two-five, tells the story of George, a lovely pet dog who promises to be good when his owner is out.
Kate was seen looking at some artwork and books on Friday
Doting mum Kate also revealed she "loved" a brightly coloured rug from a children's ward featuring a character from one of Haughton's books.
Both George and his sister Princess Charlotte love being read stories by their parents. Prince William previously revealed that his children were fans of Julia Donaldson's Room On The Broom.
The book tells the story of a friendly witch who invites animals to join her on her broom, and help the witch when she is threatened on their journey by a dragon. He told fellow parents during an engagement in south Wales: "I read this to our children all the time."
William has even met the author when she received her CBE for services to literature, and said to her: "Do you realise how many parents you have saved at bedtime?"
The royal was gifted the Oh No, George! book, £5.54, Amazon
The author's other popular book, The Gruffalo, is also frequently read in the Cambridge household, and during William's meeting with her, he said: "I know who you are. It's a big hit in our household."
Thanks to their grandad, Prince Charles, the two royal children are big fans of the Harry Potter franchise. In 2018, the future King spoke about his relationship with his grandchildren in BBC One documentary Prince, Son and Heir: Charles at 70.
During the programme, the Duchess of Cornwall revealed that her husband has a talent for narrating stories. "He reads Harry Potter and he can do all the different voices and I think the children really appreciate that," she said.
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