Around 2,000 people from the Don't Extradite Assange campaign assembled at Lincoln's Inn Fields, close to Holborn, before marching past Parliament Square at around 6pm on Saturday.

Assange has been detained at HMP Belmarsh in southeast London since he was expelled from the Ecuadorian embassy in 2019, after being holed up there for more than seven years.

He is currently fighting extradition to the United States after submitting an appeal to the European Court of Human Rights in December.

Assange's wife, Stella, addressed crowds at a rally in Westminster, holding up a scarf made by one of her husband's most loyal supporters, the late Dame Vivienne Westwood.

Mrs Assange said the carnival made "a big impact on central London" and hailed the "incredible" response.

"We need to keep building until the movement is so big that those in power and the courts realise that there is nowhere else to go than to free Julian," she said.

The husband of Nazanin Zaghari-Ratcliffe, Richard Ratcliffe, also appeared on stage.

"I'm here as a point of hope," he said.

Other speakers included former Labour leader Jeremy Corbyn; WikiLeaks editor-in-chief, Kristinn Hrafnsson, and Dame Vivienne's son, Ben Westwood.

The late fashion designer's son described how he and his mother visited Assange in the Ecuadorian embassy on a number of occasions, revealing how he walked the catwalk in a fashion show held in the building in 2014.

The procession was led by a huge golden effigy of Lady Justice, often seen blindfolded and carrying a sword and scales, a statue of whom stands on top of the Old Bailey.

Some campaigners also dressed as the statue while others depicted prisoners and judges with flashing red noses.

Many also opted for colourful carnival attire as they banged drums and held up placards with slogans including "Hands off Assange - don't shoot the messenger".

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The Don't Extradite Assange campaign tweeted that it had a "fantastic turnout" for the event.

National coordinator, John Rees, said the group has a "responsibility to make sure this case doesn't fade from the public eye".

"Julian Assange has been convicted of absolutely no crime, and justice delayed is justice denied," he said.

"The newspapers that collaborated with Assange have written a joint letter supporting his release, and he has the support of most major human rights organisations in the world.

"This is unprecedented and in most cases this would have been enough to have him freed.

"I hope our action tonight will help put pressure on the British and American administrations to free Julian Assange."