A former lover of Princess Diana has allegedly attempted to sell two cards sent to him by a young Prince William. Former Cavalry Officer James Hewitt reportedly tried to sell the cards to an American memorabilia dealer based in Los Angeles for £15,000 each.

According to The Times, the 57-year-old offered to sell the cards to Gary Zimet last month through a friend. Hewitt, the former lover of the Princess of Wales, had previously attempted to sell a wider collection of private letters written by Diana and Prince William.

One of the cards is a thank you note sent by the prince in April 1988 with a photo of five chimpanzees labelled "Mummy, Reg, Harry, Ruth [and] William." The card, which was signed "with love from William and Harry," thanked Hewitt for a "lovely morning" that included playing snooker, climbing on tanks and playing with guns, The Times reported. The second card was a birthday card with well wishes for Hewitt.

Zimet told The Times that he reached out to Hewitt last year by addressing a letter to "James Hewitt, Devon". The 62-year-old, who runs Moments in Time, said he did not hear anything from Hewitt until October, when he received a call from Hewitt's friend Alan Darlow. Darlow, a Welsh property dealer and play producer, asked Zimet for a valuation of 45 cards and letters sent to him, The Times reported.

"He said James will sell the letters. I think he mentioned a figure of £150,000," Zimet said. However, the card and letter sale fell through when Zimet was unable to find a buyer. "There's bad juju about them" he said. "A lot of people don't want to touch them. The irony is, about three months ago a person approached me who had a client, but James didn't want to sell. I guess he became paranoid about the possibility of publicity."

Zimet added to The Mail on Sunday, "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."

Then in July, Zimet said he received a message from Darlow saying that "unfortunately there is no deal unless 100k-plus privately." According to The Times, Darlow encouraged Zimet to keep in touch if he found someone interested because Hewitt was not offering the letters and cards anywhere else.

In October of this year, he received another email from Darlow with the offer for the two cards from the prince. The Times reported the email read: "Hi Gary, just spoken to James. If you personally want the two William and Harry cards he wants 15,000 each." However, Darlow emailed Zimet again this week, claiming Hewitt was "totally fed up" with Zimet's persistence and claimed he did not wish to sell anything.

This is not the first time Hewitt has attempted to sell love letters written during his five-year relationship with the princess. In 2003, he allegedly told a tabloid reporter he wanted "£10 million for the lot".

According to the Daily Mail, when confronted by a "damning email trail" which proved he was behind the recent attempt to sell by The Mail on Sunday, Hewitt said he had "nothing" to say. The newspaper also reported that the letters were offered up for sale to Prince William and Prince Harry via their attorney in November 2014.