Video report from ITV News Security Editor Rohit Kachroo
British-born radical preacher Anjem Choudary, who has spent the past 20 years spreading extremist views, is facing jail for drumming up support for Islamic State.
Father-of-five Choudary encouraged backing for the terrorist group in a series of talks posted on YouTube.
Police pounced after Choudary recognised a caliphate - a symbolic Islamic state - had been created under an IS leader in June 2014.
He and three other influential radicals lent their names to an oath of allegiance to IS which was posted on the internet.
Despite being a leader figure in the banned extremist group al-Muhajiroun (ALM), Choudary stayed on the right side of the law for two decades before investigators were able to pin him down as he preached inciting messages to his 32,000 Twitter followers.
Supporters of the 49-year-old have included Michael Adebolajo and Michael Adebowale, the murderers of soldier Lee Rigby, and suspected IS executioner Siddhartha Dhar.
He now faces a maximum possible sentence of 10 years in prison.
Choudary and co-defendant Mohammed Mizanur Rahman, 33, were found guilty of inviting support for IS between June 29 2014 and March 6 2015.
The verdicts were delivered on July 28, but for legal reasons can only be reported for the first time today.
The trial at London's Old Bailey heard the preacher, viewed by officers as a key force in radicalising young Muslims, had been the "mouthpiece" of Omar Bakri Mohammed - the founder of the banned extremist group ALM.
He courted publicity by voicing controversial views on Sharia law, while building up a following of thousands through social media, demonstrations and lectures around the world.
In one speech in March 2013, Choudary set out his ambitions for the Muslim faith to "dominate the whole world".
He said: "Next time when your child is at school and the teacher says 'What do you want when you grow up? What is your ambition?', they should say 'To dominate the whole world by Islam, including Britain - that is my ambition'."
The Crown Prosecution Service said evidence showed Choudary had been encouraged to endorse IS to his followers by Siddhartha Dhar, who later left the UK to fight with extremists.
Choudary, of Hampton Road, Ilford, and Rahman, of Sidney Street in Whitechapel, east London, will be sentenced on September 6.
Video report from ITV News Security Editor Rohit Kachroo.