A letter that Princess Diana wrote for her friend Dudley Poplak from 30 years ago is going up for auction in Cornwall. The letter is quite short but the auctioneers estimated it will fetch at least $760 (£600) because it had a "very poignant" message.

The Princess of Wales apparently wrote to her friend about what her next 10 years will bring after she thanked him for his birthday present. She also wrote that she has learned "a great deal" in her past 10 years. 

Princess Diana had been married to Prince Charles for nearly a decade at the time she wrote the letter. The note also came just six years before she died tragically in a car accident in France. 

Two years before the letter was written, Princess Diana confronted Camilla Parker-Bowles on her affair with Prince Charles. She also went on public television to tell the world that there were three of them in her marriage to the Prince of Wales. 

Poplak was a friend of Princess Diana through her mother, Frances Shand Kydd, who was commissioned to work on Prince Charles' Highgrove House in 1981. Poplak, a staunch ally of Princess Diana, died in 2005 at the age of 74. 

Written on a Kensington Palace notepad, Princess Diana's letter came from a retired manuscript and autograph dealer. It was dated June 27, 1991, or four days before Princess Diana turned 30 years old.

Meanwhile, more than 23 years since her death, Princess Diana remains a popular member of the royal family. The enigmatic royal had the power to move people with the words she spoke.

In 1995, Princess Diana sat down with BBC to speak about her life as a royal and the recognized wife of the future king. It was a no-holds barred interview that reportedly shook the British monarchy because she finally let out the biggest open secret: her husband was in love with another woman.

In that same interview, Princess Diana also said that there are people who did not want her to become the queen so she would rather be the "queen of people's hearts." According to reports, Princess Diana had a way with words because she learned from her step-grandmother, the famous novelist Barbara Cartland. 

Following that BBC interview, Queen Elizabeth finally told Prince Charles and Princess Diana to divorce. They were living separately for more than three years before the Queen stepped in.