Prince Harry was "constantly in trouble" while at boarding school, letters sent by Diana, Princess of Wales, to a favoured Buckingham Palace steward have revealed.
The personal notes, sent to Cyril Dickman in the 1980s and 1990s, include a description of how in the days after Harry was born Prince William was inseparable from his baby brother - and gave him "an endless supply of hugs and kisses".
As well as revealing details about the private life of the young family at Kensington Palace, the messages show how fond Diana was of Mr Dickman, who provided her with support after the death of her father in 1992.
The six handwritten notes are part of a collection described as "the private letters between a trusted butler and the royal family" that is expected to sell for thousands of pounds at auction later.
Diana said it was a "particularly happy time" in a letter sent five days after Harry's birth in September 1984.
She wrote: "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 October 1992 she wrote to Mr Dickman ahead of a trip to Asia with the Prince of Wales.
"The boys are well and enjoying boarding school a lot, although Harry is constantly in trouble!" she wrote, adding: "We are off to Korea in November for a visit so a good place to do the Christmas shopping!"
John Foster, of Cheffins auctioneers in Cambridge, said interest in the collection had been "phenomenal", with enquiries coming from as far afield as Japan, Australia and Canada, but he admitted how much they may sell for "is anyone's guess".
He told the BBC: "One of the nice things about this collection is that it reveals the personal side, it's not just thanking someone for an event, it's things like the handwriting and the squiggly drawings.
"There is also mention of when Diana's father passed away and how sad it was, talking of the children when they were at school, how much trouble they got into, just those personal touches which you never really get to hear about."
Among the letters is a note appearing to wish Mr Dickman well on his retirement in 1992.
In it she wrote: "Cyril, you will be greatly missed by this particular Lady - thank you from the bottom of my heart for being so kind to me throughout the years and take great care of yourself, fondest love from Diana x."
The collection also includes photos, Christmas cards and a boxed piece of cake from the Queen's wedding in 1947.
A note sent by the Queen thanking Mr Dickman for his condolences following the death of her sister, Princess Margaret, in February 2002, will also be auctioned.