Princess Diana's ex-lover, James Hewitt, decided to cash in on his relationship with the late princess and put her love letters in auction — an act that can be considered as a betrayal for the British palace.

According to People, Hewitt, a former household cavalry officer who had an affair with the late princess 20 years ago, is discreetly selling Lady Diana's love notes through a friend. Gary Zimet, owner of Moments in Time, a Los Angeles-based seller of historic autographs, confirmed Hewitt's participation in the deal.

In auction are the princess' eight personal letters, 32 greeting cards as well as six-year-old Prince William's letters to her mother. Daily Mail reports that the former member of the British army is planning to sell the items to the highest bidder in the U.S.

For the most part, Zimet said that the letters' tone is nothing but friendly. In one of the letters, Princess Diana reportedly joked and dubbed herself a "demented lady" as she wrote to her ex-lover.

"I think you are very brave to take this demented lady on," the letter reads, dated in Dec. 19, 1987 in a Kensington Palace stationary.

However, Daily Mail further says that there are some letters in auction that showcased a rather flirtatious Diana, giving a reason for the British palace to seize the letters since they can give a negative impression to the late princess.

"Dearest James, you have left and it all feels very empty here to me and that includes one bottle of champagne too," the princess' letter reads, dated March 4, 1988. The letter's entirety has been chosen not to be publicized, out of Daily Mail's respect to the British palace.

Further, it was reported that Diana's ex-lover has exerted so much effort in discreetly selling the memorabilia in order to milk some cash from his five-year relationship with the princess. When Hewitt was asked on whether or not he is behind the auction, the 57-year-old declined the allegation. However, when an email trail was presented to Hewitt confirming that he is the one selling the letters, he just kept mum and said he had "nothing" to say.

"From the start I was told secrecy and privacy was paramount. That no one must know James was behind the sale of these letters. I was told it had to be hush-hush and that James wanted absolute privacy and discretion," Zimet told Daily Mail.

In November last year, the letters were reportedly sold to Princes William and Harry. A total of 64 love letters were reportedly at the hands of Hewitt, and, in 1993, he revealed that he is planning to sell the collection for £10 million.