It is unclear why any of the U.S. agencies would have eavesdropped on Diana'a phone calls, though some in Britain said they don't think it would be out of the question.
"She actually had put herself in a very high-profile political position," Seward said. "I think it probably would be odd if she wasn't being monitored."
For example, Diana was a vocal campaigner for a ban on land mines.
"Perhaps it's that link that made her of interest to outside intelligence services," said Crispin Black, a former British government intelligence analyst. "That doesn't mean it was something sinister."
According to reports, Lord Stevens will also confirm that Diana's driver that night was a French intelligence agent, with the DST (Direction de la Surveillance du Territoire). London newspapers are saying that Stevens traced $200,000 that had amassed in 14 bank accounts, though no payments have been linked to Diana's death.
"If I were an FBI man or a DST man or a MI5 man, I would make sure I had drivers in all the big hotels in the big cities working for me," Black said.
The latest in conspiracy theory was reported today in the London Evening Standard, citing members of a French family who witnessed the crash.
They claim that one of the cars left the scene at high speed and a taxi stopped at the entrance to the Alma tunnel, where the crash occurred.
The family said British investigators have never asked them about their firsthand knowledge of what happened.
The report will be carefully studied by royal coroner Dame Elizabeth Butler-Sloss, who is due to reopen formal inquests into the deaths of Diana and Dodi in the new year. She reversed herself last week when she announced that hearings would be public.
Along with the many adoring Diana fans, Mohamed Al Fayed welcomed the decision, saying he "will not tolerate any further attempts being made to sweep dirt under the carpet and conceal the truth."
Meanwhile, Prince William and Prince Harry announced today that they would mark the 10th anniversary of their mother's death with a pop concert.
The princes said the concert, for 90,000 fans, would include Diana's favorite performers from Britain and the United States, including Sir Elton John, who sang a special version of "Candle in the Wind" at Diana's funeral.
Prince William said the main purpose is to celebrate and to have fun; he said he wants the event to "be full of energy, full of the sort of fun and happiness which I know she would have wanted. And on her birthday as well, it's got to be the best birthday present she ever had."