Simon Dorante-Day has shared new photo evidence that he believes proves he is the secret son of Prince Charles and Camilla.

He has fought for decades to prove his claims that he is their biological son and has taken his battle to the Australian High Court.

Dorante-Day was born in the UK and believes that he was conceived when Prince Charles and Camilla were romantically linked to one another the first time when they were just 17 and 18 respectively.

“My grandmother, who had worked for the Queen, told me outright that I was Camilla and Charles’ son many times,” he told 7NEWS.com.au.

His latest photographic evidence has many people convinced.

The photo shows Dorante-Day's son compared to the Queen when she was in her early 20s.

“We were blown away when we first saw it,” Dorante-Day explained.

“Elvie and I feel like we see many members of the royal family in our children, but this one was an eye opener,” he added.

“One of my supporters did the comparison and sent it to me and I was speechless.

“A lot of people are reacting to it because it’s hard to deny the similarity.”

His supporters were shocked by the side by side images as well.

“I thought that too, when I saw Liam’s photo yesterday. I have followed your quest for a few years now Simon and I admire your integrity and the integrity of your wife Dr Elvianna. I just know that the truth will be told," one supporter wrote.

Daronte-Day has also said that he was devastated by the passing of Prince Philip.

“For us it’s also mourning a lost opportunity,” he said.

“I would have very much valued the opportunity to talk with Philip but as Elvianna pointed out - his DNA will live on in the children and I.”

“Since Philip’s death, people are seeing so many photos of him and many are stopping me in the street to say how much I look like him,” he said.

“Even people who see me regularly are blown away. It’s become quite overwhelming, just how many people are talking about the similarities.”

“We owe it to our children for them to have answers,” he said.