Prince William gave a group of schoolchildren a special treat during an engagement in Oxford when he revealed some special facts about his two youngsters, Prince George and Princess Charlotte. William spent several minutes in conversation with the pupils from Pegasus Primary School about their favourite lessons and books.

He spoke of his family's fondness for one children's book in particular. Schoolgirl Xiomara, eight, told reporters: "His favourite book was The Gruffalo."

When asked if the Julia Donaldson book was a favourite with William, or his son George and daughter Charlotte, the schoolgirl added: "His and his children."

William was also given a drawing of a toucan before he headed into Oxford University's Weston Library. The Prince was given a tour of the space before making a speech and unveiling a plaque to mark its official opening.

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Earlier in the day, William also debuted the newly renovated and extended Longwall Library at Magdalen College.

The plaque unveiled by the 33-year-old commemorated the library's original opening by the Prince of Wales, later Edward VIII, in 1932 when he was a student at the college.

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William spoke to a group of students who helped raise $740,000 towards the almost $14 million cost of the project.

"Do you actually use the library? This isn't just for show then?" he joked. He then fondly recalled his own student days at the University of St Andrews, where he met his wife Kate.

"I hope you all get firsts [first class honours degrees]," William added.

Before leaving William stopped to chat to a group of college scouts, who are responsible for cleaning the students' rooms. "How messy are the students? Do they have all the files in one corner and the clothes in the other?" he asked. "I know students!"

His last engagement of the day took him to the Blavatnik School of Government, the first of its kind in the country, which the Prince called "a community gift to Oxford". The Prince met those involved in the design and construction of the new building.