Prince Charles was questioned by Scotland Yard for several hours last week about the death of his first wife, Princess Diana.
The princess, divorced from Prince Charles, and her boyfriend, Dodi Fayed, the son of the owner of the upscale department store Harrods, died on Aug. 31, 1997. Their chauffeur-driven Mercedes went out of control as it was pursued by photographers in a Paris road tunnel. The driver, Henri Paul, was killed, and the couple's bodyguard, Trevor Rees-Jones, was critically injured.
Prince Charles was formally interviewed by Scotland Yard as part of its original investigation. They reportedly questioned him for several hours about events leading up to deaths.
The French inquiry into the princess's death found that it was an accident. The French blamed Diana's driver, who they said was driving under the influence of alcohol.
So far, the $5 million British investigation has already been one of the costliest in the nation's history.
Before her death, Diana apparently wrote a letter saying she believed Prince Charles and his friends were plotting her death.
"My husband is planning 'an accident' in my car, brake failure and serious head injury," she wrote, speculating it was "to make the path clear for him to marry."
Her butler shared the letter with the public a few years ago.
"We are frankly mystified," said British royal biographer, Robert Lacey. "This document was talked of as a letter. If it is a letter, we don't know at the moment who the princess was writing to -- with whom she shared this extraordinary allegation."
According to Lacey, one of the late princess's friends told him Princess Di often sought advice from mystics and wrote down on sheets of paper what they told her they saw.
"Maybe that's what this sheet of paper is," Lacey said.
This time around, Lord Stevens, the investigator who questioned Prince Charles, allegedly asked about his response to the "bizarre allegations that he had been part of a plot to murder Diana."
Royal coroner Michael Burgess ordered the inquiry into Diana's death more than two years ago "to separate fact from fiction and speculation."
Prince Charles' spokesman said, "We are not going to comment in any way on the detail. But we don't want to mislead anyone. We've got nothing to hide. We always said he would talk to Lord Stevens, and I can confirm that that has now taken place."