Paul Burrell told the inquest Dodi Fayed's courtship was an "exciting time" for the princess in 1997, it was his understanding Diana was deeply in love with Dr. Hasnat Khan, a heart surgeon at the Brompton Hospital, The Daily Mail reported.
The princess, Fayed and their chauffeur died in a Paris car crash on Aug. 31, 1997.
"This was a very new friendship which (later) developed into something more," he said.
Mohamed Fayed has claimed Diana was pregnant and soon to marry his son when they were "assassinated" to stop the marriage and birth.
Medical examiners said Diana wasn't pregnant when they performed an autopsy, and various government officials have denied Fayed's conspiracy theory.