Princess Diana’s death is still a mysterious one?

Princess Diana was murdered because she planned to expose Britain's role in the deadly arms trade, according to a leading defence lawyer.

Michael Mansfield QC claimed that she was planning to publish a diary replete with details of those closely involved with British land-mine manufacturing.

"Everyone remembers she raised the profile of the land mines.

"Everybody is aware that the British involvement in the arms trade, particularly land mines, is and was a huge vested interest.

"It seems to me she had planned various visits. She had already been to Angola and she was going to Cambodia.

"A large number of land mines had been manufactured by the British. She claimed she had an explosive diary in which she was going to expose the people most closely involved in the British arms trade," The Daily Express quoted him as saying in the Hay Festival in Powys, Wales.

Mansfield said her anti-land mine campaign and plan to reveal the secrets behind the trade were "not unrelated" to the car crash in Paris on August 31, 1997 that killed Diana and her boyfriend Dodi Fayed.

He also spoke of a witness who claimed that the diary existed along with a missing box of papers that could contain crucial information.

He told a Spanish newspaper, "Diana had given interviews attacking the Royal Family but what most annoyed the authorities was that she became very actively involved in the campaign against land mines."

A spokeswoman for Princes William and Harry said they had "no comment" on the latest allegations surrounding their mother's death.