The Duke of Cambridge has visited a Vietnamese primary school to learn how children are being encouraged to protect endangered rhinos - with the help of a story book.
William is on a two-day official visit to the Asian country to highlight the damaging effects the illegal trade in wildlife has on some of the world's best-loved animals like the rhino and elephant.
In the capital Hanoi, he joined a class at Hong Ha primary school, where the youngsters were reading I'm A Little Rhino - one of a series of books produced to educate children about endangered animals and why they are threatened.
The book tells the story of a young white rhino growing up in Africa, who describes their way of life and how they are targeted by poachers because some people wrongly believe their horns have healing properties. It ends with a strong plea not to buy the animal parts.
William was pictured at a table with a group of children reading the book, and later posed with a large number of youngsters for a photograph.
Teresa Telecky, the book's author and wildlife department director for the animal protection organisation Humane Society International, which co-produced the publication, said: "We are thrilled that Prince William is helping to bring attention to the plight of rhinos and the dire poaching crisis they face, which is decimating their wild populations in Africa and Asia.
"Driving the crisis is the demand for rhino horn for its use in traditional medicines and health tonics despite the horn having no medicinal value.
"Our I'm A Little Rhino book educates children about rhinos and the threats to their survival and encourages them to ask adults in their lives not to buy or consume rhino horn."
During his visit to the school, William, who is president of the Football Association, found time to play football which some of the children as their classmates watched, and clearly enjoyed himself.
He later toured the old quarter of Hanoi, visiting medicine shops and a cafe as part of his efforts to encourage the work of Vietnamese people to stop the use of things like rhino horn in traditional medicine.
While its use is reported to be declining, traditional medicine is still a strong part of Vietnamese culture.
On a walk down Lang Ong Street, the home of traditional medicine, the Duke was shown round one of the many shops lining the narrow road to understand more about the properties of the plant-based ingredients used in traditional medicines.
In one of the premises he was shown some of the medicinal plants and other substances being sold, and held a handful of one up to his nose to smell the aroma.
Before leaving the district, William joined traditional medicine experts, activists, journalists and NGOs in a typically Hanoian coffee shop for a discussion about social attitudes towards the use of illegal wildlife trade products and what actions the individuals are taking to help change them.
Vietnamese singer-songwriter and wildlife activist Thanh Bui said: "Having travelled to South Africa and experienced the tragic plight of the rhino first-hand, I can only condemn the barbaric trade in rhino horn.
"As a nation, Vietnamese people must take action to protect these critically endangered animals by not buying or using rhino horn."