Prince Louis had a heartbreaking reply when he was told of his great-grandmother's passing.
Speaking to mourner Banita Ranow outside Windsor Castle today, Princess Kate said she welled up when she told her three children, Prince George, 9, Princess Charlotte, 7 and Prince Louis, 4, of the sad news.
The Sun reported the Princess of Wales also revealed the heartbreaking reply her youngest son had when he learnt of Queen Elizabeth's passing.
The four-year-old prince who stayed close to the monarch during her historic Platinum Jubilee earlier this year reportedly said, "At least granny is with great grandpa now."
Prince Louis made headlines in June after he stole the show at the late Queen's Platinum Jubilee.
Standing on the balcony beside Her Majesty for the traditional appearance at Trooping the Colour, the young prince captured the hearts of the world with his hilarious toddler antics.
Louis beamed and chatted to his great-grandmother as they watched the show from the balcony of Buckingham Palace, before dramatically covering his ears as the planes flew overhead.
Kate was seen whispering in little Louis' ear – as he frantically waved up above at the passing aircraft.
Prince Louis and his older sister Charlotte then continued their playful waves while the rest of the royal family grinned at the adorable children.
Queen Elizabeth passed away on September 8 at 96 years old. Buckingham Palace released a statement soon after her passing revealing she died "peacefully" at Balmoral.
Since her passing, her son, Charles, has been named King while his wife, Camilla has assumed the title of Queen Consort.
Earlier today the new Prince and Princess of Wales – William and Kate – were seen greeting mourners outside Windsor Castle with Prince Harry and Meghan Markle by their side.
It was the first time the "fab four" have been seen together since Commonwealth Day on March 9, 2020 and is thought to signal the end of the brothers' bitter feud.
The Sussexes' friend, journalist Omid Scobie, later said on Twitter that the invitation was made at the "11th hour". However, hinting that William was prepared to extend Harry an olive branch and work towards melting the ice between them, he declared: "It is, without a doubt, a significant moment in the history of the relationship between the two brothers".
The unexpected show of unity by the quartet followed King Charles' mention of his "love" for the Duke and Duchess of Sussex during his maiden speech on Friday.
The new free open-air saltwater pool is already proving popular.