WHILE thousands have suffered from Al Qaeda’s brutality, few understand its inner workings as well as Aimen Dean, a former operative turned British spy.

From 9/11 to London’s 7/7 attacks, the terrorist group is linked with some of the most vicious atrocities of the 21st century. 

The dad-of-one was 17 when he met Khalid Sheikh Mohammed, the mastermind behind the 9/11 attacks, which killed almost 3,000 civilians. 

He had just emerged from a year battling the Serbs in the Bosnian war, where he was exposed to “charred remains, mutilated bodies, and mass graves”.

Speaking exclusively to The Sun, Aimen revealed he was lured in by the promise of fighting a “villainous” America who he blamed for the lengthy war.

But he turned on them when he saw the true face of the terror group – appalled by how they would indiscriminately slaughter civilians.

Aimen was speaking to us as this week Britain marked 20 years since 7/7 – where 52 people were killed and 784 as bombs went off across the London Underground and on a bus.

“He was so convincing, he was so eloquent that I believed what I now know were delusions,” he said.

‘Kill or be killed’

Aged 18, Aimen travelled to a secluded mountainous spot in Afghanistan where he would spend the next 11 months learning how to build bombs.

As a self-confessed bookworm and “nerd”, the intellectual rigour and mathematical precision required for bomb making proved an exciting – albeit risky – endeavour for the teenager. 

“I remember thinking this is so much fun, why didn’t they teach chemistry like this at school?” he said.  

Joined by three other men – including Moez Fezzani, now an ISIS leader in Libya – he spent his days mixing highly toxic chemicals under the watchful leadership of vengeful chemist and terror mastermind Abu Khabab.

Khabab was in charge of developing Al Qaeda’s mass-casualty weapons and was linked to a series of terror plots before being killed in a CIA drone strike in 2008.

Outside of building bombs, the group spent their time debating and listening to the radio.

“We would just sit down and discuss everything endlessly. We would talk about what is wrong with the world.

“We would reinforce each other’s negative views and talk about the need for change and how this could only come if we tear the system down,” Aimen recalled.

With just a mattress on the floor to sleep on and little else but books to keep him occupied, the bunker was basic at best. 

I remember thinking this is so much fun, why didn’t they teach chemistry like this at school?

Aimen Dean

Bombs and extremely toxic chemicals were stored in wooden shelves, which Aimen joked would have given any British health and safety inspector a heart attack.

He said: “We were dealing with chemicals all the time so they gave us lots of fruit to build up our resilience.”

“Khabab told us that your first mistake is your last mistake. He had two missing fingers to which I said, well you are testament of living to make another mistake. 

“He said: ‘it’s idiots who came before you who did this. They are no longer here anymore – I was just collateral damage'”.

Your first mistake is your last mistake

Terror leader, Abu Khabab

But just under a year after Aimen joined the terror group, his life took a drastic turn when news of a suicide bomb attack in East Africa upended his views and beliefs. 

The devastating assault on U.S embassies in Nairobi, Kenya and Tanzania resulted in 200 deaths and an estimated 4,000 wounded. 

According to Aimen, some 150 civilians were also blinded because the vans were “loaded with shrapnel” to maximise death and destruction.

New beginnings

“This is when I started to have doubts and I realised things were going in the wrong direction.

“I realised it was about making gas canisters full of hydrogen cyanide to attack nightclubs and cinemas,” he said.

“My good moral compass and critical thinking kicked in.

“I thought, what if I build something for someone that is then used on civilians? I disagreed completely with this,” he added.

When he raised his concerns with Khaleb, the terror leader replied: “The world is not the Disney movies that you watch.

“This is a jungle. Kill or be killed. The world only respects one language: terror.”

Feigning sickness, Aimen was sent to Qatar where he renounced his oath to the terror group and decided he would never go back. 

I started to have doubts and I realised things were going in the wrong direction

Aimen Dean

Arriving in the country, he was questioned by security services as a suspected Al-Qaeda member.

He cooperated by giving them a number he had memorised for an Al-Qaeda bank account.

Delighted at having landed on an treasure trove of intelligence, the Qataris offered him the choice of being handed over to America, France or Britain.

“I felt little cultural affinity with the French and didn’t speak the language. And I didn’t trust the Americans either,” said Aimen.

Within nine days he had “landed in the lap” of MI5, who he said enthusiastically whisked him back to the UK after quickly recognising his impressive knack for map reading and photographic memory. 

Arriving in the UK, he was offered a Coca-Cola which he tried for the first time (now, his favourite drink) and a Harry Potter book.

The next six months were filled with long training days and getting to grips with English before being sent to live in a flat with an Al Qaeda operative in London.

On becoming an informant for the British Secret Intelligence Service he said the best piece of advice he received was to just “go and have fun”.

During this time, Aimen hopped between homes and became close with his roommates by leaning on his superior intellect and offering them religious guidance.

He said: “I am generally theologically better trained than the average Al Qaeda person so I ended up being kind of like a spiritual coach.

“It’s a bit brutal but it means they will open their hearts and minds to me, which made my espionage much easier.”

It wasn’t long before Aimen was asked if we would go back to Afghanistan and acquire intelligence for the MI6.

This is a jungle – kill or be killed. The world only respects one language: terror

Abu Khabab

After rigorous training, he returned to the Middle East pretending his return was so he could get back in touch with his spirituality.

He spent the next eight years spying for MI5 and MI6, becoming one of the secret service’s most audacious spies.

When asked about any close calls, he told The Times about a period in 2001, when he was called to meet one of bin Laden’s closest lieutenants.

He feared they had clocked on but was instead asked to deliver a message to four “brothers” in London, instructing them to “leave the country”.

The message read: “They must leave the country and come here before September 1. Something big is going to happen and we expect the Americans to come to Afghanistan.”

Aimen was walking along Oxford street later that year when he learned of the terror attack on America’s Twin Towers and remembered those haunting words: “something big”.

Not long after, he caught wind of a worrying plot engineered by his former leader Khabab to bomb the New York Subway.

Thanks to Aimen’s tip, news of the planned attack was passed to the Oval office and successfully foiled.

When asked about any close calls, he recalled the time he was cooking at the military camp and suddenly felt the cold end of a pistol against his lower spine.

“Someone said, that’s it confess, we know who you are. We know who you are working with,” he said.

His thorough training had taught him how to detect a bluff, so he held his nerve.

It later transpired the incident was a routine test. Did he ever feel scared? Nervous, yes, he said.

But the trick is to always “forget you’re spying”.