As long ago as 2003, Princess Diana's lover James Hewitt announced he wanted to sell his letters from the princess for £10m ($15m).

Now, according to US memorabilia dealer Gary Zimet, Hewitt has again been offering the 45 letters and cards from the princess during their five-year affair.

Hewitt's friend Alan Darlow contacted Zimet last year.

Is Hewitt 'betraying' Diana?

"I think he mentioned a figure of £150,000," explained Zimet, who runs Moments in Time, reports the Times.

But when Zimet couldn't find a buyer, Hewitt seems to have had a rethink. Last month he asked Darlow to contact Zimet with the offer of two cards from princes William and Harry written in the 80s.

"Hi Gary, just spoken to James. If you personally want the two William and Harry cards he wants 15,000 each," read Darlow's email.

At Paul Fraser Collectibles we are surprised Hewitt's offer of £150,000 ($226,600) was not met with a buyer. We've seen single Princess Diana letters sell for more than £9,000 ($13,600). And the revealing nature of this correspondence from this most absorbing of affairs makes for fascinating reading.

"Dearest James, You have just left & it all seems very empty here to me & that includes one bottle of champagne, too! It was wonderful to see you," writes Diana in one of the letters from 1988.

The £15,000+ ($22,660) figure for the cards from the princes is more fanciful.

While there is great interest in correspondence from Prince William and Prince Harry, and their signatures are terrifically rare, values are nowhere near that level. We suggest a figure of £7,500 ($11,330) each is more appropriate.

Sarah, Duchess of York, has previously criticised Hewitt's attempt to sell the letters. "Betrayal, I think is the most horrible, horrible, disloyal thing you can do to anyone", she told CNN's Larry King.

See our stunning collection of Diana memorabilia for sale.

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