Simon Dorante-Day has gained worldwide fame after going public with his claims that he is the secret love child of Prince Charles and Camilla.

After decades of research, Day has come out with new claims that Princess Diana knew about his existence as well.

“We believe that Diana knew of my existence, that she had put together the pieces,” he said to 7NEWS.

“Diana was at a point where she was finding out answers about her life, how she was wronged – and she was going public with it.

“I wrote to Mohamed Al-Fayed, Dodi’s father, with my story and told him who I was.

“One of Diana’s secret fears would’ve been that there was a secret child. There were all sorts of rumours flying around, and my existence would’ve been one of them.”

He said that investigators were also interested in the claims and demanded he sends a fax outlining his research at 2 am.

“We were in Lismore, NSW, in 2004 after Diana,” he said.

“I sent a letter to the Metropolitan Police saying I believed I was Charles and Camilla’s son and whether it would have any ramifications in the case about Diana’s death.

“And at 2 am they asked me to write a statement and fax it back as soon as possible.

“I was making submissions to the Paget Enquiry and as a result, Charles got questioned a second time during the enquiry – and it was after my letter was sent, and I believe this is why.”

Unfortunately, Diana never confirmed or denied his existence in the years before her death.

“Diana sadly died before I went public with my claims, so she was never publicly asked about me,” he said.

“But I believe my birth and adoption was part of a royal cover-up. Through her investigations into Charles and Camilla, she would’ve heard the rumours of my existence and made enquiries. How could she not?”