Writing in The Sun on Sunday, Ms Seward said the Princess “trailed off into a giggle” after making the ominous comment.
The biographer then claimed: “(Diana) even thought Prince Charles wanted her out of the way and had penned a note saying as much and even suggested Camilla was a decoy and he wanted the way clear to marry their children’s nanny Tiggy Legge-Bourke.
“But now a year later she knew all her fears sounded silly and she was full of life and vivacious, positive and at ease. By nature, she was an incredibly insecure person.
“It was one of her greatest problems — she would never outgrow the habit of dropping her eyes when she spoke in her silvery, little-girl voice, but she seemed more at ease with herself.”