Heartwarming unseen letters from Princess Diana which reveal about Prince William and Prince Harry’s childhood are up for auction.

The notes are being sold by the family of the late Cyril Dickman, who served as a palace steward at Buckingham Palace for more than 50 years. The collection of letters will be auctioned off by late Cyril Dickman’s familyIn one touching letter, dated March 2, 1985, Princess Diana revealed Prince William’s delight after Prince Harry was born in September 1984, writing: “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!”

She also spoke of how she and Prince Charles had been ‘overwhelmed’ by the reaction to Harry’s birth and could ‘hardly breathe from the mass of flowers’.

Another letter, dated July 18, 1993, reveals the naughty side of Prince Harry, then aged eight.

Diana wrote: “The boys are well and enjoying boarding school a lot, although Harry is constantly in trouble!”

Prince Harry was a pupil at private Ludgrove School in Berkshire at the time and the letter shows his cheeky spirit which is his signature trait.

Mr Dickman died aged 85 in 2012 and the letters were uncovered by his grandson. Other items in the auction include signed Christmas cards from Prince Charles, Queen Elizabeth II and Prince Philip, with the lot valued at £15,000.

Mr Dickman started his career at Buckingham Palace watching out for fires on the roof during the Blitz.

The high esteem he was held in by Princess Diana is reflected by the fact she confided in him about the death of her grandmother, the Baroness Fermoy, in July 1993.

In a letter dated July 18, 1993, she writes: “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.”

Mr Dickman retired at the age of 65 and was made a Freeman of the City of London.

In 1993, Mr Dickman was advisor to Sir Anthony Hopkins for his role as a butler in the film 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’.

Dylan Mander, specialist at Cambridge-based auctioneers Cheffins which is auctioning off Mr Dickman’s letters, said: “Cyril’s grandson came in and said while he was going through everything he found all of these amazing letters from Princess Diana.

“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.”