on her son and successor, King Charles III, who ascended to the throne automatically upon her death.

As the first new UK monarch in 70 years, Charles faces a number of challenges in the years ahead, as he tries to modernize the monarchy and overcome a mixed public image he had as Prince of Wales.

But on top of that, the new king is now facing an unusual new legal and personal issue: an Australian man claiming to be his son.

For years, Simon Dorante-Day, a 56-year-old man from Queensland, Australia, has been making tabloid headlines by claiming he is the secret son of King Charles and his wife Camilla.

According to 7NEWS, Simon was born on April 5, 1966, in Gosport, Portsmouth, and was adopted by a couple named Karen and David Day. His adoptive grandparents Winifred and Ernest Bowlden both worked in the royal household of Queen Elizabeth and Prince Philip.

But his adoptive grandmother dropped a bombshell by telling him his real parents were actually Prince Charles and Camilla. “She didn’t just hint at it, she told me outright,” he told 7NEWS.

While Charles and Camilla didn’t marry until 2005, their close relationship goes all the way back to the 1960s. They maintained a well-known affair while they were both married — a major factor in Charles’ crumbling marriage to Diana.

Thus, Simon believes that he was conceived by the couple when they were teenagers, and the royal family covered it up to avoid a scandal and arranged an adoption under fake names. While the royals have refused to acknowledge his claims, he’s spent decades trying to prove his case.

He’s won some support from the public — several images comparing him to members of the royal family, alleging a close resemblance, have gone viral and convinced people online that there are truth to his claims.

The death of his “grandmother” Queen Elizabeth II, and the ascension of Charles to the throne, has only added more fuel to Simon’s mission.

The Queen’s death was a moment of complex emotions for Simon. He was sad over the Queen’s passing, but also sad that she never responded to his letters, and that a “window of opportunity has closed,” he told 7NEWS.

Still, he saw it as an opportunity to turn his attention to his “dad,” the new King Charles: “I’m not dealing with her any more, I’m dealing with him.”

And in a new development, Simon is saying he will try to bring legal action against the king, taking him to court in order to get a DNA test.

“There has been a discussion in there between a judge and myself and his barrister about the legal standing of Charles, and whether the monarch is protected by the law or is above the law,” Simon said. “And the answer to that was no – they told me that we don’t see any reason why he is.”

“And secondly, Camilla and her family are certainly not above the law. So that argument’s already been had and settled.

He says that a judge told him that if he presents his evidence in court, there is no reason for them to deny his application for a DNA test, and Charles and Camilla will have to answer, even if they are King and Queen.

In recent days, Simon has also felt some resentment towards his possible half-brother, Prince William, who was declared Prince of Wales and next in line to the throne.

But if Simon’s claims are legitimate, he is Charles’ first-born son, and technically it is his birthright to be in the line of succession.

“It’s hard not to take Charles naming William as the Prince of Wales as anything other than a kick in the face,” he told 7NEWS. “He gives William a title like that, well where’s my answer? Where’s my DNA test? If you are not my father, then prove you’re not.”

“I feel dismissed. Charles got what he wanted: he got the throne, he got his wife, he got it all. I don’t even get the truth about my mother. When’s it going to swing the other way? Now it’s time for me to get my happy ending.”

Simon is certainly determined to prove his case, and has convinced a lot of people of his legitimacy. This “bombshell” could a PR headache for King Charles III in his early days as the new monarch.