Radical cleric Anjem Choudary, long a thorn in the side of British authorities, was jailed Tuesday for five-and-a-half years after being convicted of encouraging support for Islamic State (IS) jihadists.
Supporters of the 49-year-old and his co-defendant Mohammed Mizanur Rahman -- who received the same sentence -- shouted "Allahu Akbar" (God is greatest) from the public gallery as the judge announced his decision, according to an AFP journalist.
Judge Timothy Holroyde said Choudary was "calculating and dangerous" and had shown no remorse in a ruling handed down at London's Old Bailey court.
Dressed in a white robe, Choudary showed no emotion as the sentence was passed.
"A significant proportion of those listening to your words would be impressionable persons looking to you for guidance on how to act," said the judge.
Sue Hemming from the Crown Prosecution Service said both men were "fully aware that Daesh (IS) is a proscribed terrorist group responsible for brutal activities and that what they themselves were doing was illegal."
A jury convicted both men in July.
Choudary is the former head in Britain of Islam4UK or al-Muhajiroun, a now banned group co-founded by Omar Bakri Muhammad that called for Islamic law in Britain.
For two decades, the former lawyer who is of Pakistani descent, managed to stay on the right side of the law, becoming Britain's most prominent radical preacher.
Among those radicalised by Muhajiroun were the suicide bombers who killed 52 people on London's public transport system in July 2005, and the men who murdered soldier Lee Rigby in the capital in 2013, police say.
Commander Dean Haydon, head of counter-terrorism at London's Metropolitan Police, earlier said: "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 organisations."
He said an oath of allegiance made in July 2014 was a "turning point", giving police the evidence they needed to prove that the men supported IS.
The father-of-five previously hit the headlines for organising a pro-Osama bin Laden event in London in 2011.
He also belonged to a group that burned poppies, the symbol of remembrance for deaths in war, during an Armistice Day protest in the British capital in 2010.