Duke's letters read to Diana jury

The correspondence between the Princess and "Dearest Pa" sheds light on the Royal Family's attempts to save her marriage to the Prince of Wales as it broke down in 1992. But the coroner, Lord Justice Scott Baker, ruled that only heavily-edited versions of the lengthy letters could be released to protect their intimate contents.

And the Duke was not required to give evidence to the inquest in person, instead sending his private secretary, Brigadier Sir Miles Hunt-Davis.

In the letters Diana thanks Prince Philip for his "heartfelt and honest" words and praises his "marriage guidance skills". In one, she writes: "Even if you are unable to succeed in this, I still would like you to know how much I admire you for the marvellous way in which you have tried to come to terms with this intensely difficult family problem."

For his part the Duke promises in one letter that he will, if invited, "always do my utmost to help you and Charles to the best of my ability".

The inquest also heard that Diana was not planning to get engaged to her new lover Dodi Fayed, with whom she died in a car crash in a Paris underpass on August 31 1997.

Her close friend and confidante Rosa Monckton, who went on holiday with her a fortnight before her death, said the Princess was "excited" about her relationship with Dodi. But she said Diana was really pining for her heart surgeon ex-boyfriend, Hasnat Khan, from whom she had recently split.

"It was clear to me that she was really missing Hasnat and that I think Dodi was a distraction from the hurt that she felt from the break-up of that relationship," she said.

Dodi had showered Diana with gifts, but this made her uneasy, the inquest heard. "She said 'I know that he's going to give me a ring, but that's going to go firmly on a finger on my right hand'," Ms Monckton said.

Ms Monckton also ruled out the possibility that the Princess was pregnant when she died, saying she had her period just 10 days earlier.