Diana thought she was being spied on by Dodi's father, sister says

The sister of Diana, Princess of Wales, says Diana feared her boyfriend's father was spying on her as the couple took a luxurious Mediterranean cruise.

Lady Sarah McCorquodale told an inquest investigating the deaths of Diana and her boyfriend Dodi Fayed that her sister believed the yacht the two were vacationing aboard had been bugged by Dodi's father, Mohammed Al Fayed.

McCorquodale told the London court that Diana shared the concern during a phone conversation from the yacht.

She said she assumed the princess was talking over a mobile phone.

Diana, Dodi Fayed, and their driver, Henri Paul, died in Paris after their car slammed into a pillar in the Pont d'Alma tunnel on August 31, 1997.

While French and British investigators blame Paul for the crash, Mohammed Al Fayed maintains the couple fell victim to a plot carried out by rogue intelligence agents and masterminded by Prince Philip, the Queen's husband.

Much of the testimony at the inquest has centred on the question of whether anyone was eavesdropping on the princess, and the nature of her relationship with Philip, her father-in-law at the time she was married to Prince Charles.

Earlier Monday, a British detective said a box allegedly containing letters addressed to the princess from Philip remains missing.

Acting Det. Insp. Roger Milburn said the whereabouts of the box, which he said contained correspondence between the two, remained "an unanswered question."

McCorquodale also said she had no idea where the letters had gone.