In a legal victory for millionaire Mohammed al Fayed, a British court Friday ruled that the inquest into the deaths of his son Dodi al Fayed and Princess Diana in a 1997 car crash should be heard by a jury.

Three senior judges at the high court in London, in an unprecedented legal action, overturned deputy royal coroner Baroness Butler-Sloss's decision that she would sit alone without a jury in determining what caused the deaths of Diana and Dodi Fayed in Paris nearly 10 years ago.

The judges ordered that the coroner hearing the inquest "shall do so sitting with a jury". Mohammed al Fayed, the owner of Harrods departmental store, had challenged the coroner's decision to preside without a jury over the inquest arguing that her decision to act alone gave the appearance of impropriety.

The princess, 36, and her boyfriend Dodi Fayed, 42, died when their Mercedes crashed in the Pont de l'Alma tunnel in Paris as they sped away from pursuing paparazzi. Al Fayed said he is "certain" Diana and Dodi were murdered.

Justice Smith, sitting at London's High Court with Justice Collins and Justice Silber, made clear that Lady Butler-Sloss, if she continues hearing the case, cannot sit as the royal coroner.

"We quash the decisions to conduct the inquests as deputy coroner for the Queen's Household and without summoning a jury," the judges said. The latest development may delay the start of the inquest scheduled for May.