After a decade-long investigation costing the taxpayer more than £12m, the jury concluded that Diana and her lover Dodi Fayed died because of the "grossly negligent driving" of Henri Paul and a group of photographers pursuing their car.

The 11 jurors emphatically rejected the claims of Dodi's father, Harrods tycoon Mohamed al-Fayed, that the 1997 car crash in Paris was a murder plot.

Their findings were immediately dismissed by Mr al-Fayed who, having stormed out of the High Court in London when the verdict was given, later reacted with a shrug and said: "The most important thing is it is murder."

Mr Paul was killed along with Diana and Dodi when their Mercedes crashed into a pillar in the Alma underpass in Paris in the early hours of August 31, 1997.

After almost 24 hours of deliberations, spread over four days, the jury concluded that Mr Paul had been drinking and was going too fast, as earlier investigations by French and British police had found.

Jurors also singled out the photographers' speed and manner of driving as contributory factors, but they decided Diana and Dodi might have survived the crash if they had been wearing seatbelts.

Among other elements the jury listed as contributing to the fatal crash was the design of the tunnel, following evidence from road accident experts that the impact of the 65mph crash was more intense because the Mercedes struck a pillar rather than a wall.

By a majority of nine to two, the jury opted for full verdicts of "unlawful killing" attributed to "grossly negligent driving of the following vehicles and the Mercedes".

The verdicts came at the end of a six-month hearing which heard evidence from around 250 witnesses, including Hull-born Kieran "Kes" Wingfield, a bodyguard who was protecting Diana on the night she was killed.

The jury went a step further than the finding in 2006 of former Metropolitan Police Commissioner Lord Stevens, who ruled the crash was a "tragic accident".

Mr al-Fayed has long claimed the crash was no accident but a murder plot planned by the Duke of Edinburgh and MI6 – something for which coroner Lord Justice Scott Baker said last week that there was "not a shred of evidence".

In a statement after the hearing, Mr al-Fayed said he had been in a long fight to establish the truth about Diana and Dodi's deaths and was "disappointed" by the verdicts.

"I am not the only person who says they were murdered," he said. "Diana predicted she would be murdered and predicted how it would happen, so I am disappointed.

"The verdicts will come as a blow to the many millions of people around the world who have supported my struggle, and I thank them."

British taxpayers will pick up a bill of more than £12m for investigating claims that Diana and Dodi were murdered.

The initial cost of the inquest is thought to be £3.6m, but this figure is expected to rise as the Ministry of Justice has not yet received all its invoices.

However, Mr al-Fayed said the inquest was not a waste of money because it established "many new relevant facts" that had previously been withheld from the public.

His spokesman, Michael Cole, said he was keeping "all options open" on a possible legal challenge.

However, Mr Wingfield had told the inquest that there had been a series of security failings, for which Mr al-Fayed was responsible, leading up to the crash.

Mr Wingfield, who escaped the crash because he was following the Mercedes in a second vehicle, was called a "liar" by Mr al-Fayed during the inquest, but he stuck by his story yesterday.

He said: "Whatever he (Mr al-Fayed) said about me, I think ultimately he will look at himself in the mirror and know that the role he played was quite a major one in this accident.

"He's pursued these conspiracy theories so much and put so much time and money into promoting them, and now they've just been thrown out of court."

Prince William and Prince Harry said last night that they "agree" with the inquest verdict.

In a statement they said: "We should like to thank the members of the jury at the inquests into the deaths of our mother and Dodi al-Fayed for the thorough way in which they have considered the evidence.

"We agree with their verdicts, and are both hugely grateful to each and every one of them for the forbearance they have shown in accepting such significant disruption to their lives over the past six months."


Counting the cost of the inquest »