The Prince of Wales and the Duke of Edinburgh must give evidence at the inquests into the deaths of Diana, Princess of Wales and Dodi Fayed, the High Court in London was told yesterday.

Both members of the Royal Family were described as "relevant witnesses" in respect to the circumstances that led to the couple's deaths, now being investigated by the retired senior judge, Baroness Butler-Sloss.

Michael Mansfield QC, acting for Mohamed Al Fayed, told Lady Butler-Sloss that Prince Charles had already been interviewed by police but only a summary of that interview had ever been provided to the Harrods owner.

If the police officers had taken full notes then the jury at the full inquest, which begins in May, should be shown them, argued Mr Mansfield.

Prince Philip's evidence would also be of vital importance, he said. "The Duke of Edinburgh was responsible for letters sent to Princess Diana, but he has refused to be interviewed. We would like to know whether we can go beyond that."

Mr Mansfield suggested that Mr Fayed should be told the reasons the Duke had given for his refusal.

Lady Butler-Sloss said that, if evidence were produced of a plot, she would allow the jury to consider Mr Fayed's claims about the Princess's death but she added: "If there is no evidence to support them, I shall not present them to the jury because it would be my duty not to do so."

She said she had not been given "a shred of evidence" about any of the serious allegations Mr Fayed has made about the Princess's death.

But Mr Mansfield told her: "You have it already."

Mr Mansfield made clear that both the Prince of Wales and the Duke of Edinburgh were "witnesses of relevance" Mr Fayed wanted to see give evidence.

When challenged to support any allegations against members of the Royal Family, the barrister said Mr Fayed had co-operated fully with Lord Stevens's investigation and had provided them with the evidence which the former judge had been given.

He told her: "A starting point which will undoubtedly come to light during the inquest is Princess Diana's premonitions or fears." He added: "Mohamed Fayed gave a statement to the police about this and what he had been told by Princess Diana during the summer months, about her concerns, her fears and so on. He has already provided that."

Mr Mansfield added that Mr Fayed was aware that the Princess had confided in her butler, Paul Burrell.

Mr Mansfield said there had been a lot of publicity over a letter Diana wrote to Mr Burrell.

"We say it is extremely important because the original does not appear to have been seen - certainly it has not been seen by us."

The only thing that had been seen was an edited copy that had appeared in the newspapers.

"We would want to see the original of that letter," said Mr Mansfield.

Lady Butler-Sloss said one French doctor, whom she would not identify, had been approached but had indicated he would be prepared to talk to her on the phone - "but not to give evidence". She said: "This is a serious matter, but these are French citizens with their own rights.

"I don't have power to require anyone to attend from France."

She also accepted that members of the paparazzi who were present on the night of the crash "might not be terribly anxious to give evidence".