The Welling-born radical preacher, Anjem Choudary, is facing jail time for encouraging ISIS support.
The 49-year-old Muslim, who went to Mulgrave Primary School, Woolwich, has spent the last 20 years spreading his extremist views and is seen as a key figure in the UK for radicalising young Muslims.
His supporters included Michael Adebolajo and Michael Adebowale, the murderers of soldier Lee Rigby.
Choudary’s support for ISIS, was witnessed in a series of talks posted on YouTube.
In the lectures Choudary recognised a caliphate - a symbolic Islamic state - had been created under the IS leader Abu Bakr al-Baghdadi more than two years ago, the Old Bailey heard.
Despite being a lead 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 - former supporters have been convicted of terrorism however.
As a kid Choudary attended Mulgrave Primary School, in Woolwich
He now faces a maximum possible sentence of 10 years in prison, although judge Mr Justice Holroyde admitted: "There is very little in the way of precedent in the way of sentencing.”
Choudary and co-defendant Mohammed Mizanur Rahman, 33, were found guilty of inviting support for ISIS between June 29, 2014 and March 6, 2015.
The verdicts were delivered on July 28, but for legal reasons this is the first time it could be reported.
Police pounced on Choudary, along with three other influential radicals who lent their names to an oath of allegiance to ISIS.
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 father-of-five denied encouraging his followers to back the terror group and insisted the oath had been made without his knowledge.
He said: "It is completely unnecessary.
“For the rest of the Muslims it is obedience from the heart."
Choudary has been found guilty of inviting support for ISIS
Despite protesting his innocence, he continued to express extreme views during his Old Bailey trial and refused to denounce the execution of journalist James Foley by the so-called Jihadi John, aka Mohammed Emwazi, in Syria two years ago.
He told the jury: "If you took an objective view there are circumstances where someone could be punished."
Choudary, who now lives in Hampton Road, Ilford, and Rahman, of Sidney Street in Whitechapel, east London, will be sentenced on September 6.
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