Julian Assange’s father also insisted that his son remains optimistic about the prospects of not being extradited to the United States, and that there’s still fight in him, despite his current condition.

John Shipton, biological father of WikiLeaks founder Julian Assange, has revealed the details of his dramatic reunion with his son at London’s Belmarsh prison, SBS News reports.

As Shipton explained, Julian underwent a “considerable change” since the two last met during Christmas dinner at the Ecuadorean embassy last year.

"He’s lost a bit of weight, about 20 pounds, 10 kilos, which is not good but it’s stabilised now. His movements have become fine and delicate, and he thinks through things carefully before he says them. He doesn’t speak quickly. He’s considered in what he says – well-considered", he said.

Shipton also stated that his son remains "clearly optimistic" about the prospects of not being extradited to the United States on espionage charges, and that "the fight’s still there" though "the fires are a little banked".

Julian Assange, birth name Julian Paul Hawkins, was born on 3 July 1971 to Christine Ann Hawkins and John Shipton, though his parents separated before his birth.

Recently, Julian Assange was transferred to Belmarsh prison’s hospital wing after losing "dangerous amounts of weight behind bars", with one source in the prison even claiming that "his state of mind is not great, either".

Last week, first alleged photos and a video of Assange in prison surfaced online, showing the famous whistleblower with neatly cut hair and a trimmed beard, as opposed to his unkempt appearance the day he was arrested and dragged out of the Ecuadorian Embassy.

Earlier, the US Justice Department delivered a formal request to UK authorities for WikiLeaks founder Julian Assange's extradition to the United States where he is wanted for the 2010 leaks of classified government data and has already been indicted on 18 charges bearing an up to 175-year prison term.

Assange is currently serving 50 weeks in a London jail for violating his bail conditions in 2012, when he took refuge inside the Ecuadorian embassy in London to avoid extradition to Sweden on sexual assault charges.