Two "nasty" notes Philip sent to Diana criticised her conduct and left her angry, according to complementary therapist Simone Simmons who became a confidante of the Princess.

The inquest has already heard evidence about the Duke writing affectionate letters to his then daughter-in-law as the royal family attempted to save her marriage to the Prince of Wales when it broke down in 1992.

But the therapist claims the letters, one written in 1994 and the other the following year, reveal a different aspect of the relationship between the two senior royals.

Ms Simmons first met the Princess in 1993 when the royal began attending regular energy healing sessions she ran at a clinic. The two women became friends and Diana would sometimes spend up to 10 hours on the phone to the healer, the inquest jury heard.

Ms Simmons told the hearing in late 1995 Diana had a book on graphology - the study of handwriting - and was going through her correspondence with other members of the royal family examining their styles of writing.

She said: "She showed me a couple of nasty letters as we were going though analysing things according to this book. Diana drew my attention only to two letters that really upset her. Diana read one out to me, she was furious and she was imitating the voice of the Duke of Edinburgh."

Nicholas Hilliard, representing the coroner, did not ask Ms Simmons to describe the contents of the letter but asked her whether she agreed with the suggestion: "The Duke made cruel and disparaging observations about the propriety of the conduct of Diana." The healer replied: "Yes".

She was questioned by Michael Mansfield QC, representing Mohamed al Fayed, about the notes and told him one was typed while the other was hand-written and both were signed by the Duke.

Talking about the hand-written letter that Diana read out, Mr Mansfield asked: "As far as that one's concerned, would it be correct to say extremely derogatory about her?" Ms Simmons replied: "Yes and very cruel as well," then added that the other letter left Diana "red in the face".