The father of Princess Diana's lover who died with her in a Paris car crash almost 10 years ago launched a legal challenge on Monday against the decision not to hold inquests into their deaths in front of a jury.

Mohamed al Fayed, owner of Harrods, wants to overturn a ruling by the country's former top woman judge Elizabeth Butler-Sloss last month to handle the official inquiries on her own.

Diana, 36, al Fayed's son Dodi, 42, and their chauffeur Henri Paul were killed when their Mercedes limousine smashed at high speed into a pillar in a Paris road tunnel as they sped away from the Ritz Hotel, pursued by paparazzi on motorbikes.

A three-year police investigation ruled at the end of last year that the crash was an accident and not part of an elaborate murder plot as Al Fayed claims.

The inquiry backed a French probe which concluded that Paul was to blame because he was drunk, under the influence of anti-depressants and driving too fast.

Under the law, an inquest is needed to formally determine the cause of death when someone dies unnaturally.

Butler-Sloss decided it would be inappropriate to hold the inquests, scheduled from May, in front of a jury made up of ordinary members of the public saying only a coroner could give a "careful and fully reasoned decision".

On Monday Fayed, together with the Ritz Hotel and Paul's parents, attempted to reverse that decision at a judicial review held at London's High Court.

Michael Beloff, lawyer for the Ritz, argued that, for intricate legal reasons, Butler-Sloss had no jurisdiction to sit on the case or had to consider it with a jury.

"If she can, she ought not sit, and if she sits she must sit with a jury," he told the court.

Diana's children, Princes William and Harry, who are eager to put the speculation behind them, have expressed the hope that the long-awaited inquest will be "open, fair and transparent" and completed as fast as possible.

But as he entered court on Monday, Fayed said he would "never give up" until he had justice.

"I just want to find the truth -- who murdered my son," he told reporters.

"Do you think it is fair that I suffered for 10 years to find the truth and now again the new coroner says 'no jury'.

"Why? Because they know they are hiding something they don't want to be in front of the ordinary people of this country."