All "underlying material" used to compile a police report into Princess Diana's fatal crash has been requested by the coroner investigating her death.
The inquest will take place after the 10th anniversary of the crash
The move came after lawyers for Mohamed Al Fayed, whose son Dodi also died in the Paris crash, asked to see the material ahead of an October inquest.
Coroner Baroness Butler-Sloss said she would control access to the documents.
The three-year police inquiry concluded the 1997 crash was an accident - but Mr Al Fayed believes it was murder.
His lawyers want to see the thousands of pages involved in the case.
Legal experts may also be given access to the wreck of the crashed Mercedes, medical records, computer technology, photographs and plans.
Allegations of wrongdoing
Lady Butler-Sloss said interested parties who wish to have access to the material "must provide an undertaking as to confidentiality".
She ruled: "Access to material in the following directions will be in such manner and by such means as may be directed by the coroner."
Mohamed Al Fayed claims Princess Diana was murdered
She called on Mr Al Fayed's lawyers and other legal teams to provide a list of allegations "of wrongdoing in connection with the deaths" and any evidence they have to support them.
Mr Al Fayed claims Diana was pregnant with Dodi's child.
He says they were murdered in a high-level plot involving the secret service.
But the Metropolitan police inquiry concluded that driver Henri Paul, who also killed, was over the legal alcohol limit and going too fast.
Lady Butler-Sloss said the major part of the documentation used in the police report might be available in the week beginning 7 May.
The full inquest has already been delayed until October - more than 10 years after the princess and Dodi died in August 1997.
Diana, 36, and her 42-year-old boyfriend were killed when their Mercedes crashed in the Pont de l'Alma tunnel in Paris as they sped away from pursuing paparazzi after leaving the Ritz Hotel.