Catherine, Duchess of Cambridge will read a children's bedtime story on TV.
The 40-year-old royal - who has Princes George and Louis, eight and three, and Princess Charlotte, six, with husband Prince William - will mark the end of Children's Mental Health Week on Sunday when she appears on 'CBeebies Bedtime Stories' to read Jill Tomlinson's 'The Owl Who Was Afraid of the Dark' to young viewers.
The theme of this year's Children's Mental Health Week is 'Growing Together', and the subject of the book - how others help a baby owl named Plop to overcome his fear of the dark and improve his confidence - fits into that.
It is believed Catherine enjoyed reading the full-length version of the book - which was first published in 1948 - when she was a girl and she has also shared it with her own children.
She will read the abridged version of the tale in the 10-minute segment, which was filmed in a cosy den set in her own garden in London.
Pictures released show the duchess sitting cross-legged on the ground in jeans and a cosy jumper.
Patricia Hidalgo, Director of BBC Children's and Education, said: "I couldn't be more proud to have The Duchess read a CBeebies Bedtime Story as we mark the 20th anniversary of our CBeebies and CBBC channels. It's such a special and relevant tale and perfectly represents this years' Children's Mental Health Week theme. I can't wait to see her deliver her own take on such a classic story and I'm sure our audience can't either."
Catherine is patron of children's mental health charity Place2BE and the early years is another of her big passions.
Earlier this year, she announced the development of The Royal Foundation Centre for Early Childhood, and later this month, she will be heading to Denmark as part of her work with the centre as the country is seen as a "beacon of best practice" for the 0-5 age group.