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CNN Special Report, "A Double Life: The Spy Inside Al Qaeda" Hosted by Christiane Amanpour. Aired 10-11p ET

Aired May 25, 2018 - 22:00   ET

THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.

[22:00:30]

ANNOUNCER: The following is a CNN special report.

CHRISTIANE AMANPOUR, CNN CHIEF INTERNATIONAL CORRESPONDENT (voice- over): After Al Qaeda declared war on the west, this man was a rare thing, a western spy on the inside.

AIMEN DEAN, FORMER AL QAEDA SPY: I sat down next to Osama Bin Laden.

AMANPOUR (voice-over): Undercover and foiling plans for chemical weapons attacks.

DEAN: Attack small and closed spaces, cinemas, night clubs and entertainment venues.

AMANPOUR (voice-over): A scheme to place poison on luxury cars.

DEAN: It was nicotine poison, which is one of the poisons of a car to develop --

AMANPOUR (voice-over): Nicotine poison.

Revealing a plot to attack the New York City subway system.

UNIDENTIFIED MALE: You're talking about a simple device that could have killed dozens or hundreds of people.

AMANPOUR (voice-over): Then someone blew his cover and Al Qaeda was on to him.

RICHARD BARRETT, FORMER BRITISH INTELLIGNCE OFFICIAL: The leakiness, a Russian term (ph).

DEAN: Since then I've been living under a death sentence.

AMANPOUR (voice-over): Tonight, "A Double Life: The Spy Inside Al Qaeda.

This is not just a retelling of the boldest act of terror the world has ever known.

UNIDENTIFIED FEMALE: Why are they jumping?

UNIDENTIFIED MALE: Oh, god! Oh, god! AMANPOUR (voice-over): This is the story of how one man joined Al

Qaeda, before turning on it and fighting to dismantle it, risking his life, becoming a spy on the inside. Months before the 9/11 attacks, this jihadi-turned-spy told British intelligence about a disturbing conversation.

DEAN: I was summoned to see Osama Bin Laden's deputy.

AMANPOUR: What did he say to you?

DEAN: Something big is going to happen. So he told me basically they expect the Americans to be in Afghanistan.

AMANPOUR (voice-over): He says the British immediately shared this information with their U.S. counterpart. His name is Aimen Dean. He had been living with and spying on Al Qaeda for years. The terror group was unaware that its once loyal foot soldier had switched sides.

How terrifying it must be to stay in and to keep trying to pretend on the one hand to be part of it and on the other hand to be giving information.

BARRETT: Yes, I should imagine it's absolutely terrifying. On many occasion he must always feel, oh my goodness, have I made a mistake? How will I be tomorrow?

DEAN: If your cover is blown while you are there, no help is coming.

AMANPOUR (voice-over): Dean's extraordinary story is revealed in this book, "Nine Lives: My Time as the West's Top Spy Inside Al Qaeda." He wrote it with CNN terrorism analyst Paul Cruickshank and CNN's Tim Lister.

Aimen Dean, why have you decided to tell your story now?

DEAN: I thought the time right because the predominant narrative right now is that of the extremists. They're shouting loud. I think it's time to shout back at them louder.

AMANPOUR (voice-over): But going public comes with great risks because 10 years ago, Dean's former Al Qaeda comrades discovered his betrayal and made it clear they want him dead.

And do you not worry that there are still people out there from your old life, from your old world who want to kill you?

DEAN: If they are willing to risk their lives for a cause that is diluted and wrong and mistaken, then it is my belief that we should do the same.

AMANPOUR (voice-over): The story starts when Dean was a teen-ager and shared their cause and thought he was answering that call in Bosnia. It was his generation's Afghanistan when the mujahideen defeated the Soviet invasion in the 1980s. Now, it's the 1990s and the former Yugoslavia explodes into brutal conflict. And in Bosnia, Muslims were massacred. It was ethnic cleansing and

genocide, Europe's first since World War II, and graphic videos of the bloodshed were being viewed by young Muslim boys in Saudi Arabia, boys like Aimen Dean.

[22:05:01] DEAN: We were always shown footage of the Bosnian genocide and how that was a crusade against Islam and how this is a turning point where basically Christianity is at war with Islam.

AMANPOUR (voice-over): This is how Dean became radicalized, convinced that it was his duty to go to Bosnia to protect Muslims and die as a martyr. He was just 16 years old.

DEAN: I remember arriving there in October 1994, I don't know if you were there at that time or not.

AMANPOUR (voice-over): I was.

DEAN:L So, small world.

AMANPOUR (voice-over): By 1994, I had already been covering the Balkan wars for years.

The Bosnian peace process appears to be going nowhere.

As a reporter, I witnessed some of the worst of humanity. As a jihadi, so did Aimen Dean who fought on the front lines. In one battle, his job was helping the wounded and he almost became a casualty himself.

DEAN: I heard the cries of an Arab individual. So I was going to get him out of one of the bunker and with without knowing it basically, I was pulling the wires that were linked to land mines.

AMANPOUR (voice-over): He says there were at least four land mines attached to the wire wrapped around his legs, yet none detonated.

DEAN: At that time I wasn't grateful. I was thinking basically I was denied my shot at martyrdom. Obviously the mentality was very different at that time. I wanted to be a martyr.

AMANPOUR (voice-over): Dean was a true believer, but his zealous devotion would be tested when fellow foreign fighters decided to murder their prisoners.

DEAN: You see young people from Saudi arabia, from Tunisia, from Algeria, taking their axes, taking their big knives and basically beheading Serbian soldiers.

AMANPOUR: So they killed them in cold blood?

DEAN: Yes.

AMANPOUR: And what did you think about that?

DEAN: At the time I remember I saw the ugliness of the Bosnian war and what it did to my comrades, what it did to my friends. We came to Bosnia as, you know, noble volunteers trying to save people from genocide, and here we are engaged in an orgy of blood thirsty butchery. And I remember I was told would you like to take part of it? I said no.

AMANPOUR: You stated that Bosnia really taught you the horror of war and yet you didn't go home after Bosnia, you went to Afghanistan.

DEAN: Indeed I did.

AMANPOUR (voice-over): He says he was urged to go there by Khalid Sheikh Mohammed who would later mastermind 9/11. They met as the war in Bosnia was winding down.

DEAN: I was ready to believe whatever (inaudible) Mohammed was going to say about this conflict being the stepping stone towards a greater conflict in order to liberate the entire Muslim world from what they see as the ills of American-led globalization.

AMANPOUR (voice-over): Soon after arriving in Afghanistan, Dean met the Al Qaeda leader, Osama Bin Laden.

So what did Osama Bin Laden say? What was that first encounter like?

DEAN: He was talking about liberating Jerusalem, liberating the Arabian Peninsula, liberating Iraq and Syria and Yemen and creating the caliphate.

AMANPOUR: Did you really think that he was going to liberate all these countries and places that he said he was going to do?

DEAN: All of us doubted. All of us at that time doubted.

AMANPOUR (voice-over): But a year in Al Qaeda's orbit erased all doubts. What changed?

DEAN: A lot changed in a year because when you spend a year in the camps in Afghanistan, I think the propaganda you're fed, the indoctrination you're subjected to will change your mind.

AMANPOUR: So you were brainwashed?

DEAN: Absolutely.

AMANPOUR (voice-over): The next time he met Bin Laden, Dean was ready to swear an oath of loyalty.

DEAN: When I sat down next to Osama Bin Laden, he was smiling and he emphasized the importance of this pledge of allegiance and the importance of what I'm supposed to be joining. It's bigger than us. It's going to span generations. So it is basically an eternal struggle.

AMANPOUR: Do you remember the words you said?

DEAN: Yes. The process is simple. It's a handshake and during the handshake you swear that you will fight alongside him against whoever he fights and to make peace alongside them with whoever he makes peace with, to obey him in times of ease and in times of hardship, and that god as my witness. And that's it.

[22:10:03] AMANPOUR (voice-over): Osama Bin Laden was not yet the world's most wanted man. Phil Mudd is a former deputy director of the CIA Counterterrorism Center.

PHIL MUDD, FORMER CIA DEPUTY DIRECTOR: I think there is someone in the intelligence community who knew Al Qaeda was slowly emerging but I don't remember people looking at him and saying this guy is going to become the center of the universe for United States intelligence over the next five to ten years. No way.

AMANPOUR (voice-over): Meanwhile Al Qaeda was working to develop weapons of mass destruction. Aimen Dean was assigned to work in its chemical weapons lab.

DEAN: They wanted to enable people, ordinary people, to purchase every day chemicals and to turn them into chemical weapons. It's all about simplifying the art of death, let's put it this way. And that's exactly what they achieved.

AMANPOUR (voice-over): Al Qaeda's chemical weapons facilities were a dangerous and well-kept secret.

MUDD: We had some modest knowledge but I got to tell you, I think our understanding of what they were up to was minimal.

AMANPOUR (voice-over): Next --

DEAN: If they are able to twist fate in this way, what will they do next?

AMANPOUR (voice-over): No longer believing in the cause, Dean becomes a British spy inside Al Qaeda.

DEAN: You have to atone for your sins. You have to dismantle what you helped to build. You have to do the right thing.

[22:15:00] (COMMERCIAL BREAK)

AMANPOUR (voice-over): August 7, 1998, truck bombs explode outside U.S. embassies in Kenya and Tanzania, killing 224 people, including 12 Americans. This is the opening salvo of Al Qaeda's campaign of global terror. In Afghanistan, Al Qaeda operative Aimen Dean learns of the attacks when he hears the sound of celebration.

DEAN: We started to hear a lot of fire basically, a lot of shooting in the air taking place. So we immediately rushed out of the prayer hall and saying what's happening? And they said rejoice, everyone. And of course we joined in the celebration. We shot in the air. We were shouting Allahu Akbar and we were very happy that (inaudible) Usama, Bin Laden at that time, delivered on his promise to deliver a blow against the Americans.

AMANPOUR (voice-over): But in the following days as Dean learns more about the attacks, that most of the victims were Kenyan civilians, his celebration turns to concern.

DEAN: It's the justification for that which actually scared me as much as the act itself, because I felt that if they are able to twist fate in this way, what will they do next? And then we are going into the slippery slope and it's a slippery slope because it is so full of blood, you slip on it.

AMANPOUR (voice-over): The United States retaliates, launching cruise missiles into Al Qaeda camps in Afghanistan.

BILL CLINTON, FORMER PRESIDENT OF THE UNITED STATES: Our target was terror. Our mission was clear.

AMANPOUR (voice-over): They missed Osama Bin Laden. Were you around when that happened?

DEAN: Indeed yes. In one of the camps that were bombed I was there. So, the tent where I was, there was one death and one serious injury.

AMANPOUR (voice-over): Dean was unharmed. Once again, he had defied death, but this time he wasn't disappointed because he says, he was no longer dreaming of martyrdom.

AMANPOUR: Would you say that the embassy bombings was the beginning of the end of your infatuation with Al Qaeda?

DEAN: Yes. I don't like the direction. I almost got killed. And the direction is going to get thousands -- tens of thousands, hundreds of thousands killed over the next decade or two or three. So, my thoughts started to linger on leaving.

And I started to think about going back to Saudi Arabia or to go and live in any of the neighboring countries, like Qatar or Kuwait, go into university and become a history teacher. That was the plan. What a naive plan it was.

AMANPOUR: Why naive?

DEAN: Because once you are in this game, you are never going to get out.

AMANPOUR (voice-over): Yet Dean was determined to try. So in late 1998, he put into motion his plan to get out of Afghanistan and leave Al Qaeda. He got permission from Al Qaeda to see his doctor in Qatar where previously he had been treated for malaria and typhoid. This he said, would be a follow-up appointment to make sure that he was recovering well.

DEAN: So, I boarded the flight and I arrived in Qatar and I thought that's it, I'm going to start to make inquiries about how to enroll into university and that's it.

AMANPOUR (voice-over): But a call he had made from the phone of a terrorist operative had put him on the radar of security agencies. And very soon after arriving in Qatar, Dean was taken to state security headquarters and questioned about his ties to Al Qaeda. DEAN: I was kept in that building for nine days but during these nine

days, I was very well treated.

AMANPOUR (voice-over): Well treated because he quickly decided that his best option was to cooperate and tell them whatever they wanted to know.

DEAN: And in the end they told me, look, we admire the fact that you want to leave. We admire the fact that you have supplied us with considerable intelligence on what is happening.

AMANPOUR (voice-over): Dean says the Qataris told him they could not keep him and gave him 30 minutes to decide if he wanted to be sent to France, the United States or Britain.

I decided basically to work with the U.K. intelligence services.

(BEGIN VIDEO CLIP)

SEAN CONNERY, ACTOR: Bond, James Bond.

(END VIDEO CLIP)

AMANPOUR (voice-over): James Bond movies he had seen had him thinking that the British were the most professional. The Qataris put him on a plane to London.

DEAN: As soon as we landed, and there basically waiting for me where two officials from MI5 and MI6 counterterrorism, and they greeted me in Arabic.

[22:20:04] They were very enthusiastic and they just guided me into a room in the airport.

AMANPOUR (voice-over): After several hours of being interviewed, Dean gave the agents a leather pouch.

DAN: And that pouch had discs basically, floppy discs, containing Al Qaeda's explosives, chemical weapons, biological weapons and poisons and training manuals.

AMANPOUR: How did you have that?

DEAN: Because I had them at the time. Basically I was working with the Al Qaeda's master bomb maker, Abou Habad (ph) on developing these and I was trained by him for many, many months. So, I had all of these notes with me. So, I give it to them and I said basically that this is the first gift to show that my intentions are honorable. I remember it was December 16. So for them basically it was Christmas early.

AMANPOUR (voice-over): For the British being handed Al Qaeda training manuals was a huge intelligence coupe.

BARRETT: Certainly when Al Qaeda were operating in Afghanistan, there was concern about the efforts they were making to develop poison gasses. AMANPOUR (voice-over): Dean was ready to do more than just cooperate.

He would make the dramatic and life changing decision to become a British spy inside Al Qaeda, working for the intelligence agencies MI5 and MI6.

DEAN: Because you have to atone for your sins. You have to dismantle what you have to build.

AMANPOUR: So a cover story was created for Dean that he was sent from Qatar to London for medical treatment.

So you told your buddies back in Afghanistan that you'd ended up in London.

DEAN: Indeed. And how, because the hospital in Qatar sent me there because basically of an urgent medical procedure that need to be done.

AMANPOUR: And they bought it?

DEAN: Indeed.

AMANPOUR (voice-over): Al Qaeda calculated that Dean's access to the U.K. would make him even more valuable to them. But he was busy spilling their secrets.

DEAN: It took six months of debriefing MI6 and MI5 all about the networks in the U.K, in Europe, in Saudi Arabia, in Lebanon, in Pakistan, in Afghanistan. I must have been shown, you know, at least 2,000 pictures identifying basically at least 600 suspects. So, it was a big matrix, building a matrix of all the relationships and interconnections between these groups and individuals and building an accurate picture of their camp locations, of their fund-raising capabilities, of their military capabilities, of their spread around the world.

AMANPOUR (voice-over): British intelligence also wanted Dean to provide information on the increasing number of militants in London. So they found him a place to live in South London where he says he became well-known in radical circles.

So, this is 1999, how important was London as a wannabe jihadi location?

DEAN: We used to joke and we used to call it Londonabad, that capital of (inaudible).

AMANPOUR (voice-over): That bad?

DEAN: It was that bad, yeah.

AMANPOUR (voice-over): At the time, Richard Barrett was a high- ranking British intelligence official.

In the period between the east Africa bombings and 9/11, how much chatter was there? How much did you perceive in the greater U.K. intelligence operations? BARRETT: Well, there's quite a lot of concern because there were

quite a lot of people in London who were supportive of Al Qaeda. They've stayed on the right side of the law, but I think at that time policy makers in particularly were not particularly interested in terrorism that would flow of resources, to analysis, to information collection and so on, was relatively limited.

AMANPOUR (voice-over): That's where Aimen Dean came in. He would live among Al Qaeda supporters and commute around London to report on their activities. But each time he met his handlers, they had to make sure he wasn't being followed.

DEAN: The first thing is they would tell me to go to a particular phone booth, outside of a tube station somewhere or close to it. Then when I call the number, they will give me a route to follow. And at the end of the route there is another phone booth.

I pick up the phone, I dial the number and then they will tell me either go home, which means you've been followed. I never been followed. So they would tell me, okay, proceed to this hotel or that hotel or that restaurant.

AMANPOUR (voice-over): In June 1999, Dean followed that protocol going from phone booth to phone booth. Eventually he was instructed to go to the Washington Mayfair hotel. He walked in. The agents were waiting. They had an important question for him and it would be a game changer.

[22:25:05] DEAN: Would you be willing to go back to Afghanistan? And I can tell that they were preparing for a long conversation and that they have to really work hard to persuade me and they were shocked when I said, oh yeah, that's fine. They were saying are you sure? I said yeah, I know it's risky but yes, I'm willing to go back to Afghanistan, that's fine.

AMANPOUR (voice-over): Coming up, a secret agent inside Al Qaeda. Is the risk worth the reward?

MUDD: That risk is not only that they'll be beat up. That risk is that they'll be killed.

(COMMERCIAL BREAK)

AMANPOUR (voice-over): In the summer of 1999, Aimen Dean embarks on a mission that might be his last -- returning to the Al Qaeda camps in Afghanistan, no longer a jihadi but now a spy for British intelligence.

[22:30:02] DEAN: I was talking a bus with one of my friends back from (INAUDIBLE) all the way to (INAUDIBLE). I remember thinking about I'm going to meet my comrades but this time not as a friend but I'm going to see them as targets.

AMANPOUR: His ability to live among former comrades and report on their activities would be rare and invaluable.

MUDD: You cannot replace human intelligence and the ability to get next to somebody when they are suspicious that you're trying to spy on them and they'll only talk to somebody they view as a friend. You can't replace it.

AMANPOUR: And British Intelligence would not be able to replace a secret agent like Dean if he were caught.

DEAN: I thought the only way I could survive is to basically suppress the spy in me and to basically let the jihadist in me be the dominant personality and to keep saying always I'm a jihadist, I'm a jihadist, damn the west, I'm a Jihadist, in order basically to make sure that I do not slip, I do not make a mistake.

AMANPOUR: Dean knew any misstep could be fatal.

DEAN: If your cover is blown while you are there, no help is coming. Afghanistan is a black hole as far as intelligence operations were concerned. It's just a place where you can't meet handlers, you can't transmit information. You are on your own. Once you're going in, you're lost. Once you're coming out, you're born again. If my cover is compromised, then I would have faced a tribunal and death.

AMANPOUR: Aimen Dean did face death soon after his arrival in Afghanistan, not at the hands of al Qaeda, but while fighting alongside its ally, the Taliban.

DEAN: One British-Egyptian, he was a dear friend of mine actually, because we came under an ambush from the northern alliance, we had to turn back, but he was shot in the head just next to me. I had to see him basically there completely lifeless and bleeding. And I was thinking this is really serious, it could have been me.

AMANPOUR: It really crystallized the danger that you were putting yourself into.

DEAN: Absolutely.

AMANPOUR: Away from the front line, Dean was expected to continue his work on al Qaeda's WMD program with master bomb maker abu Habab al- Asiri (ph), testing chemical weapons.

AMANPOUR: Describe some of the experiments you witnessed or took part in.

DEAN: They experimented mostly on rabbits. The rabbits made almost 80 percent of the test subjects. But they experimented on dogs. If you thought rabbits are silent creatures, wait until we do the experiments and basically you will hear them shriek.

So that was very uncomfortable. And even though I am a strong-minded person, I ended up basically seeing rabbits chasing me, you know, in my dreams throughout my stay in that camp. And so you can tell basically that it had an impact.

AMANPOUR: And what -- they just died? They shrieked and died? DEAN: Of course. Bleeding from their mouths and from their noses. It was awful. It was disgusting. But nonetheless, because of my undercover assignment, you can't basically say, no, don't do it, please, I don't want to take part in it. You have to witness that.

AMANPOUR: In late 1999, all of that experimentation culminated in a frightening success that could threaten an untold number of innocent lives.

DEAN: Abu Habab (ph) was able in the end to come up with a breakthrough where he created a simple and easy-to-make device in which you can even time the device to go off to spread chemical gases.

AMANPOUR: What is this device called?

DEAN: Al-Mubtakkar, which means the invention.

AMANPOUR: How did al Qaeda plan to use these?

DEAN: The concept was to attack small and closed places. Cinemas, night clubs, and entertainment venues. However, in some cases, they wanted to attack even transportation systems, especially the underground transportation system.

AMANPOUR: It wasn't lost on Dean that he had helped terrorists perfect a weapon of mass destruction.

And what did you feel being in Afghanistan partaking in the development, the experimentation with this new kind of weapon?

DEAN: Uncomfortable but at the same time, you have to be there, you have to witness it, you have to see it, otherwise how can you report on it? That's the conundrum of spying. You have to witness horrible things in order to prevent them.

AMANPOUR: But before any poison gas device would be deployed, al Qaeda planned to use other unconventional weapons for the largest terror attack ever on American soil.

[22:35:02] Coming up, Aimen Dean is asked to relay a message to his jihadi brothers in the U.K.

DEAN: Before the end of August, they must come with their families to Afghanistan, because something big is going to happen.

(COMMERCIAL BREAK)

AMANPOUR: August 6, 2001, President Bush receives his daily intelligence briefing. It includes this memo titled, "Bin Ladin Determined To Strike in U.S." Over the previous two months, there had been a surge in warring (ph) intelligence indicating that al Qaeda was preparing to attack American interests somewhere in the world.

British spy Aimen Dean says one of the warnings came from him. In June, he had been summoned to meet with al Qaeda's chief of operations at the terror group's headquarters in Afghanistan. DEAN: So he asked me if I'm going back to London. And then I said yes. And he said I need you to tell four individuals who are living in the U.K. that they need to sort out their affairs before the end of August and they need to bring their families to Afghanistan before the end of August. That's imperative because something big is going to happen.

[22:40:03] AMANPOUR: Bin Laden's chief of operations also has specific instructions for Dean.

DEAN: Stay in the U.K. Do not be tempted to come and join the jihad with us here.

AMANPOUR: So he was basically telegraphing something big is going to happen, and we expect the United States to retaliate militarily.

DEAN: Indeed.

AMANPOUR: Did you ask him what was going to happen?

DEAN: I wouldn't even dare. Because that was what has been plastered over every wall in al Qaeda's compound, you only need to know what you need to know.

AMANPOUR: Just days later, Dean arrived back in London. He immediately briefed his handlers.

DEAN: They were more or less shocked to hear it. They asked me to go over the details, hours and hours describing every single second of that encounter. So they were guessing at the time that it will be an attack similar to the Nairobi and Tanzania in 1998 or USS Cole in 2000. No one even guessed that it's going to be on the magnitude of 9/11.

BARRETT: There was a certain amount of chatter that something big might go down but the details of the plot were kept really quite secret.

AMANPOUR: On September 11th, Aimen Dean was walking down a busy street in Central London when he came upon a crowd.

DEAN: Basically I saw lots of people congregating around a shop window, which was at the time basically one of the shops that sells big TVs and I looked at it and I saw one of the towers of the World Trade Center on fire. And the first thing that came to my mind was this is al Qaeda, no question about it.

AMANPOUR: What did you think?

DEAN: That the world is going to change. It will never be the same again.

AMANPOUR: Dean would remain undercover and be deployed by the British to Bahrain in late 2002. There an al Qaeda operative approached him, hoping to make use of his unique skills, the expertise he'd acquired at a chemical weapons lab in Afghanistan. This time the weapon was going to be poison gas and the target was to be New York's subway system.

DEAN: I was actually involved in that plot because I was actually invited to take part in that plot, because I was one of the only surviving people who witnessed the development of that device. So I was asked to comment on the accuracy of the diagrams and the accuracy of the ingredients and the accuracy of the measurements.

AMANPOUR: He needed to alert his British handlers and fast.

DEAN: We met in Dubai early in 2003 to discuss the ramifications and to debrief them completely about what I've learned so far. And of course they have alerted their American counterparts.

AMANPOUR: Phil Mudd was among those at the CIA informed of the plot and the weapon.

MUDD: Think New York City subway. You're talking about a simple device that almost looks like it could be contained in paint cans, easily constructed by maybe someone with a high school education that could have killed dozens or hundreds of people in a major transport hub like a subway, and reporting on it coming from a credible source. In my world back in '03, this is big news.

AMANPOUR: The attack was never launched because, according to Dean, the number two man in al Qaeda, Ayman al-Zawahiri, judged the timing was not right. Before long, western intelligence agency came into possession of the blueprints for the poison gas device. Was it viable? The CIA decided to find out.

MUDD: The assessment we had was that it could work. We actually built a device that we brought back into the CIA and a lot of people including people at the White House wanted to see it.

AMANPOUR: President Bush reportedly picked it up and said, "thing's a nightmare." Had it gone off in the New York subway system, it would have been terrifying.

MUDD: I think the panic that would have resulted from this would have been hugely significant.

DEAN: Well, of course there were more plots. The head of the al Qaeda' operation within the Middle East, he send the instructions to another cell in Bahrain to carry out an attack against the U.S. Fifth Fleet, especially their personnel.

AMANPOUR: The ring leader reached out to him.

DEAN: He asked for my help to build the chemical weapons for use in in close spaces. We're talking here about night clubs and bars to be deployed against American personnel who are celebrating new year's eve.

AMANPOUR: Wow. What did you say?

DEAN: Oh, I said yes, of course I'm going to participate. [22:44:59] I even said let's start preparing for it. And I gave him a list of the ingredients that need to be secured. Of course I fed that intelligence to my handlers in the U.K.

AMANPOUR: Having an agent at the heart of the plot gave British Intelligence a unique opportunity to identify terrorists and dismantle their network in the Persian Gulf. But before that could happen, Bahrain authorities arrested some of the plotters, including Dean.

Among those who stayed out of reach was the head of al Qaeda's global terror operations. There would be no trial for Dean because he was whisked away to London with his secret identity somehow still intact.

Next, poisoned luxury cars.

DEAN; The nicotine basically in a poison caused the person either to die or to have serious damage.

AMANPOUR: And Dean's cover is finally blown.

DEAN: I was shocked and dismayed and angry and afraid for my safety of course.

(COMMERCIAL BREAK)

[22:50:06] AMANPOUR: Aimen Dean was back in London, six years into his dangerous undercover work, when yet another terrorist with another scheme asked for his help.

DEAN: I was contacted by an individual who was heading one of the jihadist cells, and at the time he wanted to carry out a poison attack using nicotine poison, which is one of the poisons al Qaeda developed over the years.

AMANPOUR: Nicotine poison.

DEAN: A nicotine poison.

AMANPOUR: Who knew?

DEAN: Well, you can extract it from cigarettes.

AMANPOUR: The plan was to poison some of London's most affluent residents.

DEAN: A former handler that -- this individual wanted to use that poison in order to poison the car handles of luxury cars in London and start it against the rich in a way. So --

AMANPOUR: So how is it going to work? Somebody will put their hand on the handler of the car?

DEAN: Well, of course, the nicotine basically seeps into the blood vessels and then to cause the person either to die or to have serious damage.

AMANPOUR: Before they could poison anyone, the plotters were arrested. Just weeks later --

This is the worst terrorist attack in London.

A different al Qaeda cell, one Dean knew nothing about, succeeded in terrorizing the city. These are now crime scenes of course and the police are conducting their forensic investigation.

There were three suicide bombings on three different London subway trains. A fourth suicide bomber blew himself up on a double-decker bus. In all, 52 people were killed and 700 more were injured. It was Britain's 9/11.

UNIDENTIFIED MALE: At exactly 12:00 noon, the city comes to a standstill.

AMANPOUR: As the city mourned and the victims were laid to rest, Aimen Dean was determined to continue on as a spy, hoping to thwart future al Qaeda attacks. But just one year later, his spying days would come to a sudden and unexpected end.

DEAN: I remember I was in Paris taking the river boat to (INAUDIBLE). I was enjoying. It was the first real holiday for me in 11 years when I received a text message from a contact of mine inside al Qaeda in the gulf and he was telling me, what the hell is this? Go and see The Times website.

AMANPOUR: Dean immediately went into an internet cafe and looked up the Time magazine website. What he found was an article previewing a soon to be published book. The article provided information on the New York subway plot that Dean had infiltrated.

It revealed that western spy agency had been receiving accurate tips from an intelligence asset inside al Qaeda. And it disclosed one more detail that stunned Dean.

DEAN: Stupidly, they were -- the author was talking about an intelligence asset and he used my name, my real name, and calling me by my real name --

AMANPOUR: Why?

DEAN: I don't know why. But nonetheless, I was shocked and dismayed and angry and afraid for my safety, of course.

AMANPOUR: Dean's cover was blown. He immediately contacted his handlers at the British Intelligence Agency MI6.

DEAN: And they told me, come on the first train back to London. So I came back, and of course it was a crisis. And it was dealt at the highest level of MI6 at the time. But nonetheless, the damage was done.

AMANPOUR: Which meant?

DEAN: Which meant basically that I was no longer able to continue working for the U.K. Intelligence Service after eight years of diligent work.

AMANPOUR: Somebody had leaked details about him to the book's author and now western intelligence agency would lose one of their most valuable spies.

MUDD: In this case, this leak is devastating. You can't run a human informant and it's tough to get human informants inside al Qaeda or ISIS, because someone decided they wanted to talk to the press more. This is a uniquely American problem and it is a problem that we saw in this case.

BARRETT: In the United States, it is a particular problem because thousands of people have top secret clearance. The leakiness of Washington, you know, and so on.

AMANPOUR: Al Qaeda was now aware it had a spy inside its ranks but two years would pass before it finally identified Aimen Dean as the traitor. In 2008, a religious decree was issued that called for Dean to be killed.

DEAN: So I was going to be living under a death sentence.

[22:55:01] AMANPOUR: Had there been any attempts on your life?

DEAN: In September of 2016, I was supposed to go to a family wedding. I was warned that there were two individuals who were themselves al Qaeda members, harboring an ill intention towards me and they would actually attempt to do me harm. And so as a result, I aborted my trip to that wedding.

AMANPOUR: Dean would live the rest of his life looking over his shoulder and also worrying about what is now on the internet. Blueprints for the deadly poison gas device that he helped al Qaeda create.

MUDD: You look at the accessibility to devices like this for anybody who wants to build them on the internet. I think if you're in the U.S., you've got to be concerned about that.

AMANPOUR: Do you think those kind of plots are still on their agenda?

DEAN: It is on their agenda and it has actually filtered into ISIS.

AMANPOUR: The threat remains. Dean now consults on security and counter-terrorism for governments and corporations. He is determined to continue speaking out despite the risks.

DEAN: If we don't take risks while they take risks with their own lives for the sake of their cause, then they will win in the end.

[23:00:00] (COMMERCIAL BREAK)