Hate preacher Anjem Choudary has been jailed for five and a half years for drumming up support for Islamic State (IS).
His supporters in the public gallery of the Old Bailey courtroom in London shouted 'Allahu Akbar' as Choudary was sentenced.
The British-born 49-year-old backed the terrorist group in a series of talks posted on YouTube, and recognised a caliphate - a symbolic Islamic state - had been created under an IS leader after it was announced In June 2014.
Despite being a leading figure in the banned group al-Muhajiroun (ALM), and with a series of former supporters going on to be convicted of terrorism, Choudary had stayed on the right side of the law for two decades.
But the pledge of allegiance posted online was the breakthrough the police needed.
Choudary and Mohammed Mizanur Rahman, 33, from Whitechapel, east London, who was also jailed for five and a half years, were found guilty of inviting support for IS between June 29, 2014 and March 6, 2015.
Jailing the pair, Mr Justice Holroyde said the offences were serious given their influence over impressionable people at a crucial time when Muslims were looking for guidance on the IS Caliphate claims.
He told Choudary: "You did nothing to condemn any aspect of what Isis was doing at the time.
"In that way you indirectly encouraged violent terrorist activity."
He described Rahman as a "hothead" while Choudary was more "calculating" and the more experienced.
Both men were dangerous and had shown no remorse, he said.
"You are both mature men and intelligent men who knew throughout exactly what you were doing. You are both fluent and persuasive speakers."