LONDON

"I'm very happy," Reda Hassaine says, a few minutes before almost breaking down in tears. His joy comes from his role in gathering evidence against Abu Qatada, an extremist Muslim cleric said to be a key al Qaeda figure, who was arrested in London in late October, just days before Hassaine and I talked. Hassaine, 41, is an Algerian Muslim who has spied on militant Islamist groups for the Algerian Secret Service, the French, Scotland Yard's Special Branch, and MI5, the British intelligence agency. He won't be completely happy, though, until another London-based Islamist--Abu Hamza--is also behind bars.

Qatada and Hamza, he says, "raise money, encourage people to kill, claim assassinations." Hassaine knows this firsthand, he says, having seen their handiwork in Algeria and spied on them for various European intelligence agencies. Hassaine has a sad face and a stammer that improves with each bottle of Chianti, though it is fast replaced by melancholy. He chain smokes, enjoying the meal I've bought him, while he talks me through his journey from up-and-coming Algerian reporter to down-on-his-luck London ex-spy.

Hassaine's story is a reminder that Muslims themselves have been the biggest victims of the rise of Islamist extremists. It's not difficult to discern the moral in his tale: that worldwide indifference to the horrors of Algeria in the 1990s helped pave Osama bin Laden's path to the World Trade Center. Moreover, Hassaine suggests that the West has been--and probably still is--unprepared to fend off the Islamist threat, though he is not without hope.

"On the 11th of September, I was happy in one way," he admits at one point. Not that he wasn't horrified by the attacks. It's just that "for years and years I've been trying to warn people about what the Islamists are doing," he says. "Now I know George Bush is with me. Now I know Tony Blair is with me. But I have been working on this for years and years."

IN THE EARLY 1990s, during Algeria's brief flirtation with democracy, Hassaine was part of the growing opposition to the government. "They were corrupt and only working for themselves," Hassaine says. In 1990, he was elected a party official in the populist hodgepodge of opposition known as the Islamic Salvation Front, or FIS. But a few days later he resigned, after realizing that FIS leader Abassi Madani was a megalomaniac who "saw himself as the new caliph"--meaning a successor to the Prophet Muhammad and political, military, and administrative leader of the Muslim world.

"I met plenty of FIS people, and we talked about how the party should work, and then I found out what kind of people they are," he says. "They were using the election to get all the power and destroy the state." Hassaine says that after meeting Madani and the other FIS leaders he understood that they were planning on "going to war."

War? I ask. Against whom?

"Against the population," Hassaine replies.

When it became clear in late 1991 that Algeria's first multiparty election would bring the FIS to power, the military "canceled the election," Hassaine says. Soon the hotheaded pronouncements at FIS meetings were no longer just talk. The party's militant wing, the Groupe Islamique Armé, or GIA, swung into violent action. "Then started the killing. The policemen first. Then the journalists. They had lists of people to be killed."