Raine, Countess Spencer, told the inquest into Diana and Dodi's death in a car crash 10 years ago: "Diana was brought up in a quite old-fashioned way. I don't personally believe she would have considered it. It would have been out of the question for her."

The countess was responding to questions over whether Diana had ever mentioned that she was expecting Dodi's child.

She also told the coroner and the jury that Diana was on friendly terms with the Queen and the Duke of Edinburgh. Dodi's father, Harrods Mohamed al Fayed, claims the Duke plotted to murder the couple with MI6.

"Her Majesty was always extremely nice to her, which she appreciated very much," she said. "And the Duke was always extremely nice to her."

When Ian Burnett QC, counsel for the inquest, asked about the relationship, she said: "Diana had never mentioned receiving any nasty letters from him."

Lady Spencer said she and Earl Spencer, Diana's late father, became close friends with Mohamed al Fayed and she became a director of three Harrods companies.

Lady Spencer described Dodi as "absolutely charming, very sweet, very quiet, very modest, with beautiful manners".

Lady Spencer said the last time she spoke to Diana, by telephone, shortly before the couple's death in August 1997, she was "effusive and blissful" about her relationship with Dodi.

"It was at that moment that I felt it was highly likely that she and Dodi would get engaged and then married," she said.

She insisted the affair should not be written off as a "summer romance" because it was "much deeper, much more profound and much closer".

Lady Spencer also talked about how Diana was obsessed by fears that a helicopter accident might befall her or Prince Charles.

"She thought her telephones were bugged and her house was bugged and she was being watched," said the countess.

Diana was also very interested in horoscopes. "I know that she did go to different soothsayers, fortune-tellers, to such an extent that she forced me to do it because she so believed what was being told her and I had to please her.

"But there comes a moment when you have to make your own decisions and ignore what the soothsayers say.

"If they were so good, why did not one of them say 'beware the Ides of March'? Why didn't one of them foretell the horrors of the accident?"

At the end of her evidence, she urged coroner Lord Justice Scott Baker and the jury, to "solve this mystery, to tear aside everything that could be a cover-up and to sift everything that could be possible or impossible in order to allow poor Diana and poor Dodi to at last rest in peace."

Later MP Nicholas Soames, former Minister of State for the Armed Forces whom Diana allegedly "feared", gave evidence about appearing on TV to defend Prince Charles in the wake of of negative interviews given by the Princess.

He said he regretted saying on Newsnight that she was paranoid. He said: "I am not a doctor. I don't know what the true medical definition of paranoia is."

Querying why he had never apologised, Mr Mansfield said: "You actually meant what you said, didn't you?"

Mr Soames: "I thought what she said was way off beam."

He also denied having made phone calls to the Princess warning her not to meddle in the landmines issue.

The inquest continues.