LONDON -- As they tried to board a flight at Gatwick Airport in November 2002, three Arab residents of Britain were pulled aside by security agents. Police had questions about their luggage and ties to a radical Islamic cleric. After four days in custody, the men were cleared of suspicion and resumed their trip.

But British intelligence officials weren't ready to drop their interest in the men. Before the three flew out of the country, the MI5 security service sent cables to a "foreign intelligence agency," according to court testimony and newly declassified MI5 documents, calling the men Islamic extremists and disclosing their destination: Gambia, a tiny West African country.

When they arrived on Nov. 8, they were detained by Gambian and U.S. intelligence operatives, who interrogated them again, this time for a month, British and U.S. documents show. Then two of the men, Bisher al-Rawi and Jamil el-Banna, disappeared into the netherworld of the U.S. government's battle against terrorism, taken first to a prison in Afghanistan, then to the Naval detention center at Guantanamo Bay, Cuba.

The primary purpose of this elaborate operation, documents and interviews suggest, was not to neutralize a pair of potential terrorists -- authorities have offered no evidence that they were planning attacks -- but to turn them into informers.

U.S. and British efforts to infiltrate Britain's Islamic underground went into high gear after the Sept. 11, 2001, attacks, the documents show. The two men, acquaintances of the radical cleric Abu Qatada, were singled out by MI5 for threats, cajoling and offers of cash and protection if they would channel information. Although one of them offered some assistance, MI5 wanted more.

Rawi, 38, and Banna, 43, remain at Guantanamo. They have told their attorneys that U.S. and British intelligence operatives have visited them repeatedly there and in Afghanistan, renewing demands that they inform, offering them freedom and money in exchange. Both men say they have refused.

A review of hundreds of pages of documents recently released by the U.S. Department of Defense, a British court and the men's attorneys illustrates how the U.S., British and Gambian governments worked together in an operation that circumvented their judicial systems and, through a process known as extraordinary rendition, had two men incarcerated who had not been charged with breaking any law.

George Brent Mickum IV, a Washington lawyer who represents both men, acknowledged that they were friends of Abu Qatada. But he said neither shared the cleric's radical beliefs nor represented a security risk to the United States.

He said he was still trying to understand why British intelligence would engineer their seizure. "Either it was an attempt to put these guys at risk and to use them to find evidence that would implicate Abu Qatada," he said, "or it was an attempt to bring them within the closer control of MI5."

Spokesmen for the Pentagon, the CIA and the U.S. Embassy in Banjul, the Gambian capital, declined to comment for this article. MI5 has a policy of not commenting to the media.

The British Foreign Office released a statement last week denying complicity by the British government: "The United Kingdom did not request the detention of the claimants in the Gambia and did not play any role in their transfer to Afghanistan and Guantanamo Bay."

A Foreign Office spokeswoman said she could not answer questions because of a pending lawsuit seeking to force the British government to intercede on the men's behalf. On March 22, the government said it would ask for Rawi's release; its previous position was that it could not intercede for a non-British citizen.

The case has caused a political uproar in Britain. Critics say the documents show the British government has helped place people in Guantanamo, despite its claims that the prison is strictly a U.S. operation.

A parliamentary committee is investigating. "The key issue that certainly concerns me is whether our government, the British government, was involved in something that I would consider to be unlawful," said Andrew Tyrie, the committee chairman. "I don't want to live in a country that could be complicit in such abuses."

Rawi came to Britain as a teenager in 1984 with his family from Iraq, where his father had been tortured by Saddam Hussein's secret police, family members said in interviews. He attended British schools but was a self-described poor student who didn't need to find a job because his family was wealthy. He retained his Iraqi citizenship in hopes of reclaiming confiscated family property if Hussein's government ever fell.

One day after the Sept. 11 attacks, two MI5 agents knocked on the door of the house where he lived with his sister and her husband, family members said. The agents asked about Qatada, whom he knew from the mosque. "He was completely gobsmacked," said Nomi Janjua, his brother-in-law. "He said, 'What? Secret services?' I started laughing because we couldn't believe it."

Rawi agreed to become an unpaid informer, according to the family and his attorneys, a claim that the British government has acknowledged in court without elaborating. Although he kept details of his talks with MI5 to himself, British agents quickly became a presence at the family's house. They telephoned so often that his relatives complained, forcing MI5 to give him a mobile phone and meet him elsewhere.

Sometimes the contacts were unfriendly, family members recalled. Once, when he took his mother to an airport, agents pulled him aside for a long interrogation.

MI5 documents show that some agents came to have reservations about whether he was carrying out their orders. He tried to end the relationship in the summer of 2002, upsetting his handlers.

Banna, a Palestinian with Jordanian citizenship, came with his wife to London in 1994 from Pakistan. He had worked in an orphanage in Peshawar, where he met Qatada, a fellow Jordanian.

After the Sept. 11 attacks, Banna also received a visit from two intelligence agents, one British and one American, according to his wife, Sabah. The agents inquired about Qatada. He resisted their pressure to become an informer, she said, but they kept it up.

In late 2002, Banna and Rawi made plans to go to Gambia. The purpose of the trip, they have said, was to help Rawi's brother, Wahab, set up a peanut-oil processing plant. In an interview, Wahab al-Rawi said he had invested $225,000 in the venture and had recruited his brother, Banna, and two other friends as partners.

On Oct. 31, 2002, as Banna was packing for the trip, an M15 agent called at his London home and pressed him again to infiltrate extremist circles on behalf of British intelligence, either domestically or in a Muslim country.

"He did not give any hint of willingness to cooperate with us," the unnamed MI5 agent wrote in a report. "I returned to the choice which he could make; he could either continue as at present, with the risks that entailed, or he could start a new life with a new identity. . . . It was quite possible that he could find himself swept up in a further round of detentions."

In an interview, Sabah el-Banna said she didn't recall details of the conversation except that the agents assured Banna that he could fly to Africa. "They said, 'No, no -- go ahead. Good luck in your business." MI5 records confirm that Banna was given clearance to go.

The detention at Gatwick delayed the three travelers' arrival in Gambia by seven days. It has led to speculation by the men's attorneys and families that the delay gave the CIA time to position operatives in Gambia.

On Nov. 8, Wahab al-Rawi, who was already in Gambia, and a business partner drove to the Banjul airport to meet the travelers. There, all five men were taken into custody.

Gambian officials initially said there was a visa problem. But the men were soon locked up and moved to hidden locations and safe houses around the capital. American spies acted as if they were in charge, Wahab al-Rawi said. A brawny man who identified himself as Lee and said he was from the U.S. Embassy spent days questioning the men. He wanted to know about their ties to Qatada, whether the peanut business was a front for terrorist activities and whether they hated Americans.

Wahab al-Rawi said he refused to cooperate at first, demanding that he be allowed to contact a lawyer and the British Embassy. "Lee said, 'Who do you think asked us to arrest you? Where do you think this information came from, the questions we are asking you?' " Wahab al-Rawi said.

After four weeks, Wahab al-Rawi and one of the business partners -- both British citizens -- were released and put on a flight back to London. A third partner, a Gambian citizen, also was let go. But Bisher al-Rawi and Jamil el-Banna were flown to Afghanistan.

They have given their attorneys this account of their arrival there: They were taken to a prison near Kabul, the capital, and kept in the darkness for two weeks, with loudspeakers blaring music around the clock. Later they were transferred to a prison at Bagram air base.

Rawi and Banna said they were asked by CIA operatives in Afghanistan whether they would serve as informants, said Mickum, their attorney. Banna was offered increasing sums of money and a U.S. passport to work for the CIA, but refused, Mickum said.

A few weeks later, they were flown to Guantanamo Bay. On March 12, 2003, Rawi wrote a sardonic letter to his family in London.

"Dear Mum and family," it read. "I'm writing to you from the seaside resort of Guantanamo Bay in Cuba. After winning first prize in a competition, I was whisked to this nice resort with all expenses paid (I did not need to spend a penny). . . . Everyone is very nice, the neighbors are very well-mannered, the food is best class, plenty of fun."

Rawi told his lawyer he was visited in Guantanamo at least six times by MI5 officials, including some of the same agents who had served as his handlers in London. They apologized for the turn of events, but asked whether he would still be willing to work for the agency if they could secure his release.

"He asked me a few questions about a few people here" in Guantanamo, Rawi said of one MI5 agent, according to a transcript of a U.S. military tribunal hearing. "He asked me, if I were released, where would I like to go? I mentioned a few places; I told him he could buy me a ticket to the moon."

In September 2004, the two were brought before tribunals that would determine whether they could be formally classified as "enemy combatants." The primary evidence against them: they knew Abu Qatada, and had wired money on his behalf to Jordan.

They were also accused of carrying a suspicious electronic device in their luggage to Gambia; British police who stopped them at Gatwick determined it was a battery charger, police reports show.

In testimony during the hearings, the detainees admitted knowing Qatada and helping him transfer the funds, which they said went to a charity. They said MI5 had been aware of all their activities and had encouraged them to interact with Qatada. They also pointed out that British police had them in custody just prior to their trip to Gambia and could have pressed charges if they were suspected of illegal acts.

"We were kidnapped in Gambia, not arrested," Banna said, according to a transcript of his hearing. "I don't even know what I have done. . . . If I were a danger to anyone, Britain would have put me in jail."

The tribunals ruled that both men should be classified as enemy combatants.

Researcher Julie Tate in Washington contributed to this report.

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