Prince George told his classmates “my father will be King so you better watch out”, author Katie Nicoll claims.

The reported comment by the 9-year-old, who is now known as Prince George of Wales, appears in a new book called The New Royals by Vanity Fair’s royal correspondent.

Nicholl claimed George, the eldest child of Prince William and Princess Catherine, and his siblings, Princess Charlotte and Prince Louis, were being raised with an understanding of the monarchy and a ‘sense of duty’, the Daily Mail reported.

“George understands he will one day be king and as a little boy sparred with friends at school, outdoing his peers with the killer line: “My dad will be king so you better watch out”.’

Prince George and Princess Charlotte played a central role in the Queen’s state funeral as they followed the coffin alongside their parents the Prince and Princess of Wales, grandfather King Charles III and other members of the royal family as it was processed through Westminster Abbey in London.

The Queen’s great-grandchildren were the youngest members of the royal family to join 2000 mourners including world leaders and foreign royalty at the service.

The funeral was the first time the children used their new titles – Prince George of Wales and Princess Charlotte of Wales – as listed in the official order of service.