By Naresh Puri
BBC News home affairs reporter
Abu Hamza was well known as a radical preacher before his arrest
Reda Hassaine was an MI5 informer sent in to Finsbury Park Mosque to spy on the infamous cleric Abu Hamza al-Masri.
"He was very charismatic, he knew how to entertain his followers.
When Abu Hamza would walk in, people would sit up, it was like going to the theatre. He was the Godfather", said Hassaine.
He said members of the congregation would watch videos of people being killed to stir up hatred of the enemies of Islam. The mosque itself turned into a market.
ABU HAMZA VERDICTS
Guilty of 6 charges of soliciting to murder
Guilty of 3 charges related to "stirring up racial
Guilty of 1 charge of owning recordings related to "stirring up racial
Guilty of 1 charge of possessing "terrorist encyclopaedia"
Not guilty of 3 charges of soliciting to murder
Not guilty of 1 charge related to "stirring up racial
"There were people there who would sell passports and credit cards and it was like having one foot in a mosque and one foot in the mafia."
This image is a far cry from the Abu Hamza who arrived in Britain as a young, westernised man with a very vague knowledge of Islam, the engineering student who soon turned into a preacher of hate.
On the 16th May 1980 he married a window dresser called Valerie Traversa and they had one child, but that ended in divorce in 1984.
He later remarried, and has seven children.
Abu Hamza was known as Mustafa Kamel Mustafa when he moved to Brighton and started a degree in civil engineering at the local polytechnic in 1986.
He went to the local mosque and asked the imam whether he could stay there and help with chores in return for a small amount of rent.
Imam Sajid was in charge at the time.
"He was a good looking man, well built and very polite but he had no understanding whatsoever of Islam," he said.
Abu Hamza continued with his studies but Imam Sajid noticed a sudden change in the student after he started mixing with Algerians at the mosque. They were part of a movement which wanted an Islamic state back home.
"Hamza would listen to the Algerians and was influenced by them. He started a study circle involving up to 10 other people and we started getting complaints about his extreme views," he said.
This, according to the imam, was when Abu Hamza's radicalisation took place.
"Hamza started to get very aggressive and he would say that Islam is superior and he would never accept man-made laws.
"I predicted that he would end up on a battlefield. I was so worried I even wrote to the police warning them about this man but nothing was done," said Imam Sajid.
Abu Hamza graduated and in 1991 went to Afghanistan, claiming he wanted to help rebuild the country.
On his return to London he became a preacher. He became an imam at a mosque in Luton in 1996 and from there he moved to Finsbury Park Mosque. He was stopped from preaching there in 2003.
Abu Hamza argues his sermons and his views have been misunderstood - he says he preached the Koran.
But Imam Sajid says Abu Hamza has given Islam a bad name, and is, in his view, a prophet of doom.