King Charles III issued a "chilling" reply when a historian congratulated him on his birthday, making reference to his grandfather King George VI.

Royal biographer Robert Hardman explained in his new book 'Charles III: New King. New Court. The Inside Story' that t King George has always "loomed large" in the monarch's mind.

This was evident when a close friend of the family said that, shortly after Charles's accession, he was offered condolences and was assured that both his mother and the Queen Mother would be "looking after him" from somewhere up high.

Hardman said that the King replied by saying "that's very kind of you, but the person whose hand I feel on my shoulder is the King".

The royal author goes on to state that when the historian Kenneth Rose was introduced to the then Prince of Wales at a Welsh Guards event on his birthday, he received an unusual reply when wishing him a happy birthday.

Hardman said: "'I offered him my congratulations as you would,' Rose later told me, 'and he said the most extraordinary thing. He replied: "I am today of the same age that my grandfather was when he died".

"Which indeed he was but it was sort of chilling really".

King George reigned from December 1936 until his death on February 6 1952. His daughter, Queen Elizabeth II, was coronated on June 2 1953 and reigned for 70 years before her death on September 8, 2022.

King Charles was just three years old when his grandfather was found dead in his bed in Sandringham House, Norfolk, from a coronary thrombosis at the age of 56.

In his book, the British journalist and author revealed how King Charles learnt of his grandfather's death and the first question he asked moments afterwards.

Hardman said: "Prince Charles, aged three, and Princess Anne, aged one, were saying with their grand-parents while Princess Elizabeth and the Duke of Edinburgh were in Africa, at the start of their round-the-world Commonwealth tour.

"The little prince heard the news of the King's death from his grandmother. As the Queen Mother later told James Pope-Hennessy, she explained to Prince Charles that the King had been found by his valet when delivering his early morning cup of tea.

"Charles listened gravely before asking: 'Who drank the tea?'".