Cheffins, a Cambridge-based auction house, said the letters formed part of 'a unique collection of Royal memorabilia'.
London: Hand-written letters from Princess Diana describing her young children, William and Harry, to a former royal aide have broken pre-sale estimates to fetch early 15,000 pounds at an auction in the UK.
The former Princess of Wales had sent the letters to late Cyril Dickman, who served as a head steward at Buckingham Palace for more than 50 years.
In them she wrote about how William "swamped" his new baby brother with "an endless supply of hugs and kisses" and how "naughty" Harry was constantly getting into trouble at school.
Cheffins, a Cambridge-based auction house, said the letters formed part of "a unique collection of Royal memorabilia".
"It was extraordinary. I don't think I have ever sold such few lots over such a long period of time because the bidding just never seemed to stop. People were bidding from all over the world on the internet," Luke Macdonald, director of fine art at Cheffins, said.
The entire Dickman collection, which also included letters from Queen Elizabeth II and Prince Charles, contained around 40 lots which were estimated to fetch around 13,000 pounds.
But they went under the hammer for around 55,000 pounds. The Diana letters, split into six lots, were expected to fetch around 3,600 pounds, but went for a total of 14,900 pounds.
In one personal letter dated 20 September 1984, Diana writes: "William adores his little brother and spends the entire time swamping Harry with an endless supply of hugs and kisses, hardly letting the parents near!
"The reaction to one tiny person's birth has totally overwhelmed us and I can hardly breathe for the mass of flowers that are arriving here!"
In another, dated 17 October, 1992, she says how both young princes "is well and enjoying boarding school a lot, although Harry is constantly in trouble!"
Some of the other items in the collection, sold by the Dickman family, included letters, cards and photographs from various members of the royal family as well as an unopened boxed wedding cake from the Queen's marriage to Prince Philip in 1947.
Described by Cheffins as "a favourite of every member of the Royal Family", Cyril Dickman had received handwritten notes from royals dating back more than 30 years.