CNN  — 

Notorious hate preacher Anjem Choudary, who led a flag-burning demonstration outside the US embassy on the anniversary of the 9/11 attacks and voiced support for jihad, has been jailed for inviting support for ISIS.

The former lawyer was sentenced to five years and six months in prison. His supporters shouted “Allahu Akhbar” as he was led away from the dock in London’s Old Bailey court.

Choudary has courted controversy over two decades, skirting the edges of the law, backing extremism but with no proof of actually inciting violence. He earned the wrath of Britain’s tabloid newspapers, making him - by his own admission – the country’s “most hated man.”

In 2014, he pledged allegiance to ISIS and its leader Abu Bakr al-Baghdadi, bringing him under scrutiny and leading to his arrest.

British authorities say they were able to link Choudary to the battlefields of Iraq and Syria; UK police say they don’t know exactly how many of the 850 Britons who have traveled there were directly influenced by him, but they say he is a “key” figure in ISIS’s recruitment drive.

“These men have stayed just within the law for many years,” Commander Dean Haydon, of the Metropolitan Police’s Counter Terrorism Command, said when he was convicted.

“But there is no one within the counter terrorism world that has any doubts of the influence that they have had, the hate they have spread and the people that they have encouraged to join terrorist organizations.”

ISIS pledge of allegiance

Despite his vocal support for the terrorist group, Choudary has previously insisted he is not a danger to the public. “I don’t pose a threat to anyone in this country,” he told CNN in 2014. “I pose an ideological or political threat, definitely.”

But authorities in Britain say Choudary has been linked to the radicalization of a string of the terrorists who have stood trial in the UK over the past 15 years.

Together with Omar Bakri Muhammad, he founded the now outlawed radical Islamist organization Al-Muhajiroun. Bakri Muhammad was later banned from the UK over links to al Qaeda.

He was pictured at a protest with Michael Adebolajo, later convicted of the violent murder of British soldier Lee Rigby, and he was linked to Siddhartha Dhar, suspected by authorities of replacing Jihadi John as ISIS executioner.

But rather than traveling to Syria himself, he has stayed in Britain - where he was born and raised – and taken on the role of a vocal supporter for ISIS and radical Islam.