Stephen Yaxley-Lennon, widely known by his pseudonym Tommy Robinson, was imprisoned for 13 months earlier this year for live-streaming outside a court in breach of reporting restrictions around a trial.
Robinson is the founder of the English Defence League (EDL), a fringe group protesting perceived threats from Islamic extremism, and he has a string of convictions on charges including assault, fraud and drugs possession.
The name he uses is that of a well-known football hooligan.
Trump in Scotland on next leg of contentious UK trip
Conspiracy theories about his case have spread wildly on social media, drawing particular attention in the United States among supporters of the so-called 'alt-right'.
The campaign spread further after Donald Trump Jr, the US president's son, retweeted a comment about Robinson. Trump himself drew severe condemnation in November after retweeting three misleading anti-Muslim videos originally posted by Britain First, another far-right group.
Steve Bannon, former White House chief strategist, defended Robinson on London's LBC radio last week, reportedly describing him off-mic as "the backbone" of Britain.
The new cause celebre of the populist far-right in Britain even breached diplomatic circles after Sam Brownback, Trump's envoy for international religious freedom, raised the issue with British ambassador Kim Darroch at a June lunch.
But anti-racism group Hope Not Hate said the notion that Robinson had been wrongly imprisoned was "incorrect and conspiratorial", calling him a "violent far-right racist".
Times newspaper columnist Francis Eliott warned that the Robinson case, allied with disillusionment over Brexit and fear of immigration, could create "a far-right revival"--all "powered by alt-right cash".
Two recent pro-Robinson protests in central London, at which some demonstrators made Nazi salutes, saw violent confrontations with police and counter-demonstrators.
US Republican Congressman Paul Gosar came under heavy criticism for speaking at one of the rallies last Saturday during Trump's visit to Britain.
"It is inexplicable for a sitting US congressman to speak at, let alone attend a rally for someone responsible for spreading as much hate and bigotry as Tommy Robinson", Imraan Siddiqi, executive director of the Arizona branch of the Council on American-Islamic Relations, said in a statement.
Robinson gained notoriety in Britain after the EDL staged demonstrations in 2013 which often ended in clashes with anti-fascist demonstrators.
He was previously jailed for using someone else's passport to enter the United States, which had refused him entry because of drug offences, and has a number of other convictions.
In May, Robinson was arrested outside a court in Leeds in northern England and pleaded guilty to the contempt charge.
He was given 10 months in jail and another three months for breaching a suspended sentence for another contempt charge related to a separate case.
Reporting restrictions are imposed in all court proceedings in Britain, and are intended to avoid media reports that could influence the jury.
Raheem Kassam, a former editor-in-chief of Breitbart News London and one-time top aide to leading Brexiteer Nigel Farage, told AFP he was working to 'internationalise' Robinson's cause and organise support rallies.
Trump's many trade wars: a summary
"When the left see an injustice, it rallies an international caucus of people together...and we don't do that enough on our side," he said, adding the shift in tactics was "just the start."
The US-based Middle East Forum--a right-wing think-tank where Kassam is a fellow--is also helping Robinson "legally, diplomatically and politically", according to its director Gregg Roman.
It has spent tens of thousands of dollars footing the bills for Robinson's defence and protests--including Gosar's trip to London.
A spokesperson for Hope Not Hate decried the increasing American interest in the case, describing Robinson as "a lightning rod for an international coterie of far-right, anti-Muslim activists and extremists".
Noting a "clear plan" by alt-right figures like Bannon "to pressure our authorities to ameliorate his sentence", he added: "These attempts to sway our legal system and the paths of justice must not prevail."
Robinson is currently appealing his sentence, with a three-judge panel set to rule by the end of the month.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ