Britain's Duke of Edinburgh once questioned why an author "killed off" a fictional cat in her children's book series.

The 91-year-old royal couldn't stop himself from asking Judith Kerr why she ended her stories about Mog the feline with the book 'Goodbye Meg' after 30 years of brightening youngster's lives.

Speaking at the Telegraph Hay Festival, fellow writer Michael Morpurgo joined Judith in reminiscing about the bizarre encounter in which Prince Philip gently scolded her decision.

He recalled: "The Duke of Edinburgh said to you, 'why did you kill off Mog?' I thought, this guy reads books!"

The short tale, published in 2002, was intended to help bereaved children and begins with the line: "Mog was tired. She was dead tired... Mog thought, 'I want to sleep for ever.'

"And so she did. But a little bit of her stayed awake to see what would happen next."

The elderly royal's love of books seems to run through the family.

His former daughter in law the Duchess of York - who was previously married to Prince Andrew - has written 16 kids books, including her latest story 'Ballerina Rosie', dedicated to her daughters Princesses Eugenie and Beatrice.

In addition to this, Philip's son Prince Charles wrote his own story in 1980 novel 'The Old Man of Lochnager', while Charles' wife Camilla acts as patron to several literacy charities.