An Australian man who believes he is King Charles’ ‘secret son’ has made a wild claim that a four-way paternity test should be done in a bid to prove his claims.

British-born Simon Charles Dorante-Day has made headlines around the world over unproven claims he is the illegitimate love-child of King Charles III and Queen Camilla.

He was born on April 5, 1966, in Portsmouth, in the UK, and was adopted at eight months old.

The 58-year-old claims that as a child, his adoptive grandmother – who worked for the late Queen Elizabeth II – told him on her deathbed that he was Charles and Camilla’s son.

The father-of-nine also claims that in the months leading up to his birth, Charles was sent to Australia to study, and Camilla disappeared from the public eye for about nine months.

With the King and Queen due to touch down in Australia on Friday, Mr Dorante-Day shared a post to Facebook last month claiming there were ‘inconsistences’ between the facial features of Charles and his sons William and Harry.

‘This comparison of William, Myself, Charles, and Harry demonstrates something very clearly, there is no consistency,’ he said, along with a photo of each of their faces beside each other.

‘The fact that the left side of my face identically matches Charles whilst neither William nor Harry’s does, raises the obvious question, just who are Charles’s real sons?

‘This is why my wife, Dr Elvianna, and I believe a four-way Paternity test is the only way to resolve this issue once and for all.

‘The truth of the game that has been played by the Monarchy, the Government, and the Establishment for 58 years needs to be exposed.’

Daily Mail Australia is not suggesting there is any truth behind his claims.

Mr Dorante-Day also took the opportunity to reshare a lengthy interview he did with Seven News on his plight to prove he is the son of the King.

Part of his claims is that there are varying reports over the ages of Charles and Camilla when they met – with Mr Dorante-Day claiming they met as teenagers, not in their early 20s.

‘I’m right, why hide the real date of when they first met? Unless there’s a reason!’ he said.

Mr Dorante-Day, who lives with his wife Elvie in Queensland, has done several interviews with media, explaining why he believes he is related to the King and Queen, including comparing physical attributes.

He also claims his kids share similar features to the children of Prince William and Kate.

He had said previously he is committed to pursuing legal action in an attempt to force the King into a paternity test.

Mr Dorante-Day’s case alleges King Charles and Queen Camilla began their close relationship in 1965, a year before his birth certificate says he was born.

However, Charles and Camilla are widely reported to have met at a polo match in Windsor Great Park in 1970.

Mr Dorante-Day insists that Camilla kept him until he was eight months old, hiding him from the world with the help of the royal family and protection officers, and claims to have been told it was a condition of the adoption that his names Simon and Charles were not changed.

The father-of-nine also referred to Queen Elizabeth II as his ‘grandmother’ at the time of her death.