Previously unseen letters from Princess Diana describe the bond between Princes William and Harry.

Prince William and Prince Harry

Prince William and Prince Harry

A series of handwritten messages from Diana to Buckingham Palace Steward Cyril Dickman between 1984 until 1993, give an insight into life with the royal princes and also reveal that Harry was "constantly in trouble" at boarding school.

Describing her and Prince Charles' reaction to Harry's birth in 1994, she wrote: "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!!

Another note in 1984 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!"

And a message from 1992 explains: "The boys are well and enjoying boarding school a lot, although Harry is constantly in trouble!"

Mr Dickman died aged 85 in 2012 and the letters have been put up for auction by his grandson.

Dylan Mander, a specialist at Cheffins' auction house where the letters 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.

"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."