Princess Diana of Wales was totally convinced that someone was going to try to murder her during a trip to an Angolan landmine, said her confidant Simone Simmons on Friday.

According to Simone, Diana believed that the so-called "men in gray suits" had prepared some mines in a supposedly cleared area she walked during her famous anti-landmine campaign in Africa.

"Please pray for me" Diana told Simone on the phone during her trip in January 1997. "I am terrified that they haven't cleared the minefield properly. I am scared they have left some live ones to blow me up."

Days later, through a menacing phone call, "a powerful establishment figure" warned her and asked her to drop the campaign.

"Drop the anti-landmines campaign, you never know when an accident is going to happen," said the caller to Diana, according to Simone's narration.

"When I listened into her conversation... I was not sure of her safety anymore," Simone added.

Simone said that Diana insisted and decided to go ahead "no matter what could happen to her".

After her trip to Africa, Diana was planning to make public a dossier about people profiting from the evil trade on landmines naming several names of powerful people.

"I believe Diana was right to fear for her life and that these people would have killed her to shut her up," told Simone to Daily Star news website.