Princess Diana and her lover Dodi al-Fayed were unlawfully killed by the grossly negligent driving of their chauffeur and paparazzi photographers pursuing them into a Paris road tunnel 10 years ago.
The jury, which had spent almost six months listening to more than 250 witnesses from around the world, reached their decision yesterday after deliberating for four days.
The jury foreman said in court: "The crash was caused, or contributed to, by the speed and manner of the driver of the Mercedes and the speed and manner of the following vehicles."
The foreman said contributing factors were: The fact that chauffeur Henri Paul's judgment was impaired by alcohol, Diana was not wearing a seatbelt and that the car hit a pillar.
"I do hope everyone will take this verdict as closure," said John Stevens, who led a British police probe into the deaths.
The presiding judge, Lord Justice Scott Baker, had specifically instructed the inquest jury to reject conspiracy theories that it was a staged accident.
Ken Wharfe, Diana's former bodyguard, told the BBC: "I was surprised. Like a lot of people, I was expecting a verdict of accidental death."
Princess Diana's sister Sarah left the court afterwards without saying anything to waiting reporters.
The inquest, estimated to have cost up to $20 million, stretched around the globe with witnesses heard by video link from France, the US, Nigeria, Kenya and Australia.
Dodi's father, luxury storeowner Mohamed al-Fayed, charged that his son and Diana were killed by British security services on the orders of Prince Philip, Queen Elizabeth's husband and Diana's former father-in-law.
"I am disappointed," Mr Fayed said in a statement after the verdict, insisting that the Queen and her husband should have been called as witnesses. "No one should be above the law."
Mr Fayed believes Diana's killing was ordered because the royal family did not want the mother of the future king having a child with his son. He alleges Diana's body was embalmed to cover up evidence she was expecting a baby.
But Lord Justice Scott Baker said Mr Fayed's conspiracy theory was "without substance".
Few details of Diana's private life were spared as friends, family, faith healers, spies, bodyguards, police chiefs and butlers were called to give their opinion at an inquest that sparked worldwide media interest.
It was delayed for 10 years because Britain had to wait for the French legal process and then a British police investigation to run their course before it could begin.
Both police inquiries concluded the crash was a tragic accident caused by Mr Paul being drunk and driving too fast.
Mr Paul was employed by Mr Fayed at his Ritz Hotel in Paris.
Under British law, an inquest is needed to determine the cause of death when someone dies unnaturally.
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