Mr Wharfe claims that the Princess “enclosed copies of adult magazines such as Playboy, Mayfair and Penthouse".
He added: “I often warned her against being too explicit about her affections in her copious letter-writing.
“If the papers were to fall into the wrong hands, I said, the truth of her friendship with Hewitt would become public knowledge.
“But Diana was in no mood to listen. Perhaps her infatuation with Hewitt was over, but she was in love with the idea of being in love with a war hero".
Mr Wharfe went on to claim that Diana said: "After Harry was born, my marriage to Charles just died.
“I tried, I honestly tried, but he just did not want me. We haven't slept in the same bed for two years."
Wharfe revealed what Diana said when she first met James Hewitt.
“It was clear from the way she spoke that she adored the man, even after the affair had cooled.
“Their first conversation felt natural, she said, and it was this that sparked her attraction. As she put it, they got along famously."