Separated by bulletproof glass 20 metres away, John Shipton can do nothing but smile or wave as his son stares down a possible extradition to the US and 175 years' imprisonment.
Julian Assange was unwell enough for the Woolwich Crown Court to finish early - at 3.36pm rather 4pm, according to Mr Shipton - on day two of his extradition hearing in London.
The 48-year-old was on Monday night reportedly handcuffed 11 times and twice strip-searched, as well as having his legal case files confiscated by guards at Belmarsh Prison.
And Mr Shipton, who cannot speak with his son during the week-long hearing as it clashes with the prison's visiting hours, was forced to watch on from the public gallery as Assange began to appear "a little disturbed or unwell".
"It's horrifying for any parent to be powerless in the face of a child's suffering," he told AAP over the phone from London.
"But I don't count the personal cost, because my son's situation is pretty dire.
"Your own worries fall way behind when your children are in an almost tragic situation - you don't worry too much about yourself.
"I hope this time the prison thought better of strip-searches and unnecessary handcuffings and the dispossessing of the court papers."
Assange was in May handed a 50-week jail sentence for skipping bail and avoiding jail while he spent seven years inside Ecuador's London embassy.
But Mr Shipton is deeply frustrated by the fact his son, currently on remand in Belmarsh prison, must walk through a tunnel into court every day this week before sitting behind a bulletproof glass partition he said was designed for terrorist trials.
"I can't understand why he's still in jail and not on bail - his family is here and he's not well," Assange's father said.
"And to continue the smearing and mobbing of Julian by asserting he's a 'common criminal' who conspired with Chelsea Manning to steal is a vile insult.
"The trial, I firmly believe, is a fraud upon the court."
The US government is trying to extradite Assange to face 17 charges of violating the US Espionage Act and one of conspiring to commit computer intrusion over leaking and publishing thousands of classified US diplomatic and military files.
The charges carry a total of 175 years' imprisonment.
But Mr Shipton said even if Judge Vanessa Baraitser set Assange free, the extradition request could potentially see his son incarcerated for a further five years as each side exhausted its avenues to appeal.
"There's no 'good scenario' to come from this - they're all bad," he said.
University of Melbourne IT researcher Suelette Dreyfus, who wrote Underground - a 1997 book detailing the lives of elite young hackers - with Julian Assange, said the hearing was a weathervane for media freedom.
"From the criticisms given by the prosecution, clearly the Trump administration would like to shrink those freedoms," she told AAP on Wednesday.
"So the court proceeding has got a big public interest component.
"But I'm also concerned extradition may be used for political purposes of retaliation against whistleblowers, publishers and journalists.
"It could become a tool of oppression, rather than the tool of justice that was originally envisaged."
Australian Associated Press