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Engineer Simon Charles Dorante-Day, 56, was adopted at the age of eight months and claims his adoptive mother told him he was the "secret son" of Charles III

Charles III, full name Charles Philip Arthur George Mountbatten-Windsor, is king and statesman and Camilla, the Daily Mail reported.

The Australian said it was a "slap in the face" to see William named Prince of Wales.

He confirmed he would continue to fight, along with lawyers, to force the king to take a paternity test.

For years, he has talked about wanting the royals to undergo a DNA test to prove his genetic heritage.

He even sought senior legal advice after a letter to the Queen detailing his plight went unanswered.

"I don't want to feel that way, but I do. I just think that the least Charles could do is give me an answer - acknowledge me. He's giving William a title like that, and where's my answer? Where's my DNA test? If you're not my father, prove that you're not," Dorante-Day said.

Charles III was also proclaimed King of Scotland, Wales and Northern Ireland

The man became popular for frequently posting photos comparing himself and his children to members of the British royal family.

Last week, Dorante-Day shared a tribute to her alleged grandmother following the death of Queen Elizabeth II.

He vowed to continue his efforts to try to establish definitively that the new ruler and his wife were his real parents.

Charles III