The Duke of Cambridge was a "godsend" to the late Princess Diana.

Prince William and Prince Harry

Prince William and Prince Harry

The golden-haired beauty gave birth to her oldest child on June 2, 1982, and the moment she found out she was pregnant was one of the happiest days of the late royal's life because she felt "lucky" she was able to have a baby and be a mother.

Speaking in a tape recording of her in conversation with author Andrew Morton, who wrote 'Diana: Her True Story', which have recently been released and obtained by the Mail Online, Diana said: "A godsend, William was conceived in October. I was told I was pregnant, fine, great excitement. Marvellous news, occupied my mind. In those days, my greatest pleasure was that I was lucky enough to have a baby on the way."

And the late royal - who tragically died in a car accident in 1997 aged 36 - has revealed she endured a "difficult pregnancy" as she battled with regular bouts of morning sickness.

She explained: "I couldn't sleep, didn't eat, whole world was collapsing around me. Very, very difficult pregnancy indeed. Sick the whole time ... and morning sickness."

Diana was offered medication to combat her sickness, which she refused to take because she didn't want her child to be born with any disability.

She explained: "People tried to put me on pills to stop me from being sick. I refused to risk the child becoming handicapped as a result. So sick, sick, sick, sick, sick.

"And this family's never had anybody who's had morning sickness before, so every time at Balmoral, Sandringham or Windsor in my evening dress I had to go out, I either fainted or was sick."

And Diana felt embarrassed by her sickness because she hadn't read her books on pregnancy to help her cope with her pregnancy.

She said: "It was so embarrassing because I didn't know anything because I hadn't read my (pregnancy) books, but I knew it was morning sickness because you just do."

However, when Diana was expecting her second child Prince Harry her morning sickness wasn't "so bad".

She added: "With Harry the morning sickness wasn't so bad. With William, it was appalling: almost every time I stood up, I was sick.

"I couldn't define what triggered it off, but obviously I felt it was a nuisance to the set-up -- and I was made to feel it was a nuisance to the set-up."