The Daily Telegraph said one of the letters to be auctioned next month was written shortly after Diana's son Prince William was born in June 1982.

"We are not sure at the moment what has hit us, except a very strong pair of lungs," the princess wrote to the servant who worked for the Royal Family from 1951 to 2002. "Both parents are making little sense, we just seem to spend most of our time gazing at this tiny person."

Diana reveals in another letter to Tallon her thoughts before marrying Prince Charles and in a separate note how she felt when she was pregnant with Prince William.

The missives are part of a collection of 694 items expected to sell for more than $400,000, the Telegraph said.

Tallon died last November at the age of 72 and a condition of his will was that the items he collected throughout his decades of service would be sold after his death and the money given to the beneficiaries of his estate.

Diana died in a Paris vehicle crash in 1997.