WIKILEAKS founder Julian Assange faces an effective life sentence in harsh prison conditions if convicted in the United States, a hearing heard today.

Eric Lewis, an expert in extradition and national security cases, told the Old Bailey that some prisoners also had their meetings with lawyers recorded by the penal authorities as a matter of routine.

The US lawyer, who gave evidence via transatlantic video link, described the investigation of Assange as “one of the biggest operations in FBI history.”

Mr Lewis’s evidence was based on his experience representing high-profile prisoners such as Abu Khatallah, currently serving a 22-year sentence for “providing material support for terrorism.”

He also described the treatment of prisoners held under “Special Administrative Measures” (Sams), a classification in which he predicted Assange would be placed.

Mr Lewis explained how these regulations require a prisoner to be kept in a seven foot by seven foot cell for 22 or 23 hours a day. 

Time out of the cell for exercise and showering is taken in the middle of the night, as other prisoners sleep. 

The later addition of multiple espionage charges was “an abuse of the federal law enforcement authority,” he alleged.

It meant that if convicted, Assange would face an effective life sentence, Mr Lewis said.

“We are looking at a sentence somewhere between 20 years, if everything goes brilliantly, to 175 years which the government could easily ask for,” he said.

He was challenged by James Lewis QC on behalf of the US government, who argued that, as Sams did not have the title “solitary confinement” it was inaccurate to describe it as such.

The lawyers did agree that it was likely that, if extradited, Assange would be held on remand at the Alexandria City Jail in Virginia and, if convicted, in the “supermax” prison in Florence, Colorado.

Assange is fighting extradition following leaks of hundreds of thousands of classified documents in 2010 and 2011.

The 49-year-old has been indicted in the US on 18 charges,  including plotting to hack computers and conspiring to obtain and disclose national defence information.

Earlier, Eric Lewis told the hearing that the Trump administration is determined to “get Assange.”

He said that there was strong evidence that Obama decided against prosecuting Assange in 2013, but that by 2018, pressure from the top was exerted to pursue the opposite course.

Judge Vanessa Baraitser adjourned the case early after a technical glitch with the video link led to US television news reports taking over the feed.

The hearing continues.