Touching unseen letters written by Princess Diana about Princes William and Harry have emerged

Diana Princess of Wales with Prince William, and Prince Harry in Austria. Photo / Getty Images

Heartwarming letters written by Princess Diana describing the tender, unbreakable bond between her two young sons - and the rebellious streak in an 8-year-old Prince Harry - have been uncovered and are going up for auction.

In an article on the Daily Mail website, the letters revealed intimate moments of their family life between 1984 until 1993 in handwritten notes to Buckingham Palace steward Cyril Dickman.

One letter dated September 20, 1984 - five days after Harry was born - reads: "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!"

Another dated October 17, 1992, notes how mischievous Prince Harry was: "The boys are well and enjoying boarding school a lot, although Harry is constantly in trouble!"

She also described how she and Prince Charles reacted to Harry's birth: "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!"

And the messages show how the long-serving Buckingham Palace steward was evidently held in high esteem by the princess, as, in one poignant exchange, she confides in Dickman about the death of her grandmother.

The letters, which are valued at £15,000 (26,700), will be auctioned in Cambridge on January 5.

In the letter following Prince Harry's birth, Diana wrote warmly: "This is just to say a big thank you, Cyril, for thinking of us at this particularly happy time, with lots of love from, Diana."

The fondness the princess had for Dickman - who served as a palace steward for more than 50 years - was clear when she penned him a letter following the death of her grandmother, the Baroness Fermoy, in July 1993.

She wrote: "Thank you so much for your lovely letter concerning my Grandmother.

"Her death came as a great shock, but it has meant an enormous amount to receive messages of support such as yours.

"I often think of you and Mrs Dickman and hope that life is treating you kindly."

Princess Diana with Prince William and Prince Harry on Harry's first day of school. Photo / Getty Images

In 1993, Dickman was advisor to Sir Anthony Hopkins for his role as a butler in the film The Remains of the Day.

Diana mentioned his star turn in one of her letters to the palace steward, saying, "I wait with interest to see the film".

Princess Diana also wished him a speedy recovery upon hearing he was ill in 1985, writing: "I just wanted to write a quick note to say how very sorry I am to hear you are not feeling well.

"We missed you yesterday at Buckingham Palace."

The letter remarking on Prince Harry's behaviour was sent when he was a pupil at private Ludgrove School in Berkshire in 1993 and shows he had a rebellious streak at a young age.

Nine years later, aged 17, he was caught smoking cannabis in the grounds of Highgrove. He came under fire again in 2005 for wearing a Nazi uniform at a fancy dress party.

Dickman started his career at Buckingham Palace watching out for fires on the roof during the Blitz. He retired at the age of 65 and was made a Freeman of the City of London.

When he fell ill towards the end of his life, Prince Charles visited him at his home.

He died aged 85 in 2012 and the letters were uncovered by his grandson who has now put them up for auction.

Dylan Mander, a specialist at Cheffins' auction house where the item will go under the hammer, said: "Cyril's grandson came in and said while he was going through everything he found all of these amazing letters from Princess Diana.

Prince William arrives with Diana, Princess of Wales and Prince Harry for his first day at Eton College. Photo / Getty Images

"The letters explained all different things - how Harry had been naughty at school and how Harry was adored by his brother who would not stop kissing him.

"It is incredibly rare to have letters from Princess Diana with such a personal touch to them.

"She would not have had friends in the sense we do so you could say Cyril Dickman was one of her closest friends."

Also included in the auction are signed Christmas cards from Prince Charles, Queen Elizabeth II and Prince Philip, slices of wedding cake from royal weddings, photographs of the royals including the Queen and Prince Philip in 1990, Diana and Charles as newlyweds and the Queen Mother.

There are also custom-made Buckingham Palace cufflinks, which come in a white box marked with Cyril Dickman's initials, and a silver cigarette case.

There is also a programme from the Queen's Silver Jubilee thanksgiving service at St Paul's Cathedral on Tuesday June 7, 1977.