Supporters see him a returning liberation hero, who revived a long-lost dream of African nationhood from his flat in faraway south London. Critics see him as a dangerous insurgent who belongs behind bars.

Like him or loathe him, though few would disagree that Nnamdi Kanu has come a long way since his days running Radio Free Biafra from a council flat in Peckham.

The 52-year-old, who leads the campaign to revive the former breakaway state of Biafra, was the catalyst for President Muhammadu Buhari’s extraordinary decision two weeks ago to ban Nigeria’s 200 million people from using Twitter.

Nigerian President Muhammadu Buhari – AFP

That in turn has sparked a global row over freedom of speech, dragging in everyone from Silicon Valley’s tech giants through to ex-US president Donald Trump – not to mention Nigeria’s millions of Twitter users.

Mr Kanu, who also holds British citizenship, started Radio Free Biafra while living in London a decade ago. The web-based pirate radio station campaigns to recreate the short-lived republic of Biafra, which broke away from the rest of Nigeria in 1967, sparking a civil war that claimed a million lives.

He returned to Nigeria in 2015, where he then skipped bail on what he claims were trumped-up treason charges. Now a fugitive, he leads the banned separatist group, the Indigenous People of Biafra (IPOB), whose armed wing, the Eastern Security Network, has been accused of attacking Nigerian security forces.

He regards multi-ethnic Nigeria as a “zoo”, declaring: “We want a free and independent Biafra or death.”

Such shock-jock rhetoric has infuriated Mr Buhari, a stern former general who fought on the government side in the Biafran war. On June 2, the president Tweeted a blunt warning to the separatists, saying: “Those of us in the fields for 30 months, who went through the war, will treat them in the language they understand.”

To Mr Buhari’s fury, Twitter then deleted his post, saying violated its “abusive behaviour” policy. Two days later, the president banned Twitter from Nigeria altogether, sparking protests from his own citizens and freedom campaigners worldwide.

Defending the decision, Mr Buhari insisted that Mr Kanu has used his own Twitter, which has 300,000 followers, “to direct his loyalists to kill Nigerian soldiers and policemen.”

The government blames IPOB’s armed wing for a rising tide of lawlessness in recent months around its stronghold in the former Biafra region of south-east Nigeria. Police officers have been killed, government buildings attacked, and in April, more than 1,800 prisoners escaped during a mass jailbreak in the city of Owerri.

A day after Mr Buhari announced the Twitter ban, the platform also deleted a Tweet from Mr Kanu’s account. It said: “Any army they send to #Biafraland will die there. None will return alive.” Mr Kanu was also banned from Facebook in February after posting a video alleged to show a pro-Biafran militia group killing cattle belonging to Fulani herders

Mr Buhari’s ban on Twitter won praise from Donald Trump, who himself was kicked off Twitter over claims that his posts helped incite the US Capitol riot in January.

“Congratulations to the country of Nigeria, who just banned Twitter because they banned their president,” he said.

Critics, however, claim that Mr Buhari has over-reacted with the Twitter ban, censoring a social media tool used by 40 million Nigerians, as well as many businesses for advertising.

They claim the real reason for the ban was Twitter’s role in the #EndSARS police brutality protests, which saw huge street demonstrations last year over abuses committed by Nigeria’s Special Anti-Robbery Squad. Twitter’s CEO, Jack Dorsey, encouraged donations to one of the leading groups of organisers.

Mr Buhari argues that the California tech moguls do not have to deal with the consequences of such protests, which saw a heavy police response.

“We have not forgotten that #EndSARS resulted in the loss of lives, including those of 37 policemen, six soldiers and 57 civilians, while properties worth billions of Naira were destroyed,” his spokesman said.

With Boko Haram still running amok in Nigeria’s north-east, and a spate of banditry and mass kidnappings in the north-east, government officials say they can ill-afford to tolerate Mr Kanu stirring another armed insurgency in Biafra.

Nonetheless, many Nigerians point out that compared to the security threats in Nigeria’s north, which have claimed thousands of lives, Mr Kanu and IPOB are small scale.

Andrew Obuoforibo, a Nigerian political analyst and podcaster, told The Telegraph: “Buhari gives other more violent groups far less attention than Kanu and IPOB. I think he’s just using Kanu as an excuse to ban Twitter because of Jack Dorsey donating money to the #endSARS protest.

“If Mark Zuckerberg had donated money too, then Facebook might be banned in Nigeria as well.”