Abu Hamza al Masri is now in a British jail fighting extradition to the United States.
And as CBS News Correspondent Mark Phillips reports, Jenvey, also known as Pervez Khan, is a major reason why.
Jenvey set up a false Web site, posing as an Islamic extremist site.
Using a pseudonym, Jenvey set up a site called Islamic News, collecting material from militant Islamic movements around the world. His intention, he says, was to flush the real terrorists out.
It was like dangling bait in the waters -- and Hamza bit.
Impressed with Jenvey's site, he started e-mailing him and more.
"I was so convincing to them that they then provided video and audio tapes of their most private meetings," says Jenvey.
The tapes were key. While Hamza, in his sermons, had often supported terrorist acts abroad, he had protected himself from British anti-terror laws by never publicly calling for violent action within the U.K.
But the private tapes told another story -- one of clear incitement to acts of terror in the U.K. and the U.S.
Here's Hamza's private advice to his British and American followers. "A land for jihad is in Afghanistan. If you are more courageous you should do another Afghanistan in your own country."
More advice, came from an audio tape: "Our people should know that we should have intifada, also uprising in our own countries more than the Palestinians do in their own countries."
The tapes provided enough evidence of apparent incitement that authorities on both sides of the Atlantic pounced.
"The arrest of Abu Hamza is a major, is a major development in the fight against terror," New York Police Commissioner Ray Kelly said in late May. "He is a real deal."
The tapes served another purpose as well. They proved that American James Ujaama, who had denied knowing Hamza when facing his own terrorist charges in the U.S., clearly did know him. This proof led Ujaama to plea bargain and provide more evidence against Hamza.
Jenvey's sting was complete.
"They sometimes say if you give a fool a piece of rope he'll hang himself, and it seems that in this case this person has done exactly that," says Jenvey.
Part II: Terror on the Web: The people promoting it and those trying to find them