An official UK police inquiry into the Paris car crash which killed Princess Diana and Dodi Al Fayed has found no evidence the couple were murdered.
Lord Stevens, who led the three-year investigation, said the 1997 crash was a "tragic accident".
The inquiry report said chauffeur Henri Paul, who also died, was speeding and over the legal drink-drive limit.
A spokesman for Mr Al Fayed's father said he does not accept the findings as questions remain "unanswered".
Michael Cole said it was "highly unsatisfactory" that up to 18 key witnesses to the crash were not interviewed by the Metropolitan Police's inquiry into the death.
He called for next year's inquests to be heard before a jury so that the evidence presented by Lord Stevens could be "thoroughly tested".
The princess, 36, and Mr Al Fayed, 42, died when their Mercedes crashed in the Pont de l'Alma tunnel in August 1997.
"There was no conspiracy to murder any of the occupants of that car," Lord Stevens said.
The findings - contained within an 832 page document - form part of the inquest into the deaths of the couple.
Mr Al Fayed's father, Mohamed, said the £3.69m spent on the Stevens inquiry was a total waste.
"I feel sorry for the taxpayers and the money that has been wasted on such garbage," he said.
"Whatever it's going to cost me, if it costs me the last penny in my purse, I'm not going to rest until I get the gangsters."
Mr Al Fayed said he would "definitely" accept a verdict by an inquest jury if it heard all the evidence.
Lord Stevens told a news conference in London the report addresses the key issues emerging from a "most complex and challenging" investigation.
The inquiry brought together 1,500 witness statements
"I have no doubt that speculation as to what happened that night will continue and that there are some matters, as in many other investigations, about which we may never find a definitive answer."
The evidence suggests Princess Diana was not engaged or about to get engaged and scientific tests showed she was not pregnant, he said.
"We have spoken to many of her family and closest friends and none of them have indicated to us that she was either about to or wished to get engaged," he said.
"Prince William has confirmed to me that his mother had not given him the slightest indication about such plans for the future."
Some 400 people, including Prince Charles, the Duke of Edinburgh and the heads of MI5 and MI6, were interviewed or contacted by the inquiry.
Referring to claims by Mohamed Al Fayed, the report said there was no evidence of a connection between the Duke of Edinburgh and MI6.
Mr Stevens said the various legal cases currently being pursued by Mr Al Fayed through the French courts are "unlikely, in my opinion, to have any bearing on my conclusion that there was no conspiracy or cover up".
He was satisfied US intelligence services had made no attempt to hold back information that could have altered the inquiry's conclusions.
"I very much hope that all the work we have done and the publication of this report will help to bring some closure to all who continue to mourn the deaths of Diana, Princess of Wales, Dodi Al Fayed and Henri Paul," said Lord Stevens.
Clarence House said later that Princes William and Harry hope the "conclusive findings" of the report will end speculation surrounding their mother's death.
Harrods department store owner Mohamed Al Fayed does want closure, spokesman Mr Cole told a news conference.
Mr Al Fayed continues to believe there was a cover-up
"He wants to think back on the summer of 1997 as a happy time, with his family and Diana's family together and everybody so content in their own company.
"But he does feel that he has a solemn duty as a parent to reveal the facts as he believes them to be."
The crash took place as the couple were pursued by paparazzi photographers during the drive from the Ritz hotel to Mr Al Fayed's flat.
A French investigation into the crash concluded Mr Paul had lost control of the car because he was driving too fast while under the influence of alcohol and prescription drugs.
Meanwhile, lawyers for bodyguard Trevor Rees, the sole survivor of the crash, said he will not be making any comment on the report or the inquest.