IN a small windowless cell lit by a single light bulb, Louai al-Sakka sits isolated from the world and fellow inmates for 24 hours a day.

His concrete box is in the bowels of Kandira, a high-security F-type prison 60 miles east of Istanbul, which was built to house Turkey’s most dangerous criminals.

The prison has been criticised by human rights groups such as Amnesty International. The guards control everything, including the cell’s light switch.

Sakka’s only visitor is Osman Karahan, a lawyer who shares his fervent support for militant Islamic jihad.

Since being convicted as an Al-Qaeda bomb plotter last year, Sakka has decided to reveal his alleged role in some of the key plots of recent years, providing a potential insight into the unanswered questions surrounding them. His story is also one of a globetrotting terrorist in an organisation that is truly multinational.

He is an enigma and, despite his involvement in three terrorist outrages involving British citizens, he is virtually unknown in this country.

By his own account he is a senior Al-Qaeda operative who was at the forefront of the insurgency in Iraq, took part in the beheading of Briton Kenneth Bigley and helped train the 9/11 bombers. He has been jailed in connection with the bombing of the British consulate in Istanbul.

Certainly, the intelligence services have shown a keen interest in the 34-year-old Syrian who says he was in Iraq alongside Abu Musab al-Zarqawi, the notorious insurgent who was killed last year in a United States air-strike.

But, as with many things in the world of Al-Qaeda, there might be smoke and mirrors. Some experts believe that Sakka could be overstating his importance to the group, possibly to lay a false track for western agencies investigating his terrorist colleagues.

Over the past three weeks The Sunday Times has conducted a series of interviews with Sakka through his lawyer. We were given a number of documents including a memoir in Arabic of his life.

So who is the mysterious Al-Qaeda operative in the concrete cell and what do his claims tell us about the terrorist network and his role within it?

He was travelling under the Turkish name Erkan Ozer – one of his 16 false identities – when he was arrested in the southeastern town of Diyarbakir in August 2005. His downfall was as a result of a nighttime explosion that caused a fire in his apartment a week earlier. When fire-fighters reached the blaze they found a do-it-yourself bomb factory with vats of hydrogen, bags of aluminium powder and 6kg of plastic explosives.

Sakka had been planning to sink Israeli cruise ships off the Turkish coast using motorised dinghies. Despite having plastic surgery to disguise his face, he was easily identified by the Turkish authorities.

Police later discovered documents linking him to the Istanbul suicide bombings that killed at least 27 people after trucks exploded outside the British consulate, the HSBC bank and two synagogues. The court indictment described him as “a senior member of the Al-Qaeda terrorist organisation tasked with special high-level missions”. It said he had met Osama Bin Laden, who had told him to organise attacks in Turkey.

But was this all? Last week his lawyer claimed his scope was much wider. “He was the nnumber one networker for Al-Qaeda in Europe, Iran, Turkey and Syria,” Karahan said.

According to the documents provided by Karahan, Sakka grew up in the ancient city of Aleppo, Syria, the son of a wealthy factory owner, and followed in his father’s footsteps by becoming the general manager of a company that sold one of Syria’s most popular washing-up liquids. But he was drawn to the Islamic cause from a young age, according to his memoir.

His politics were shaped by the conflict between President Hafez al-Assad, the former Syrian dictator, and the Muslim Brotherhood, an underground Islamic group. When Sakka was nine, Assad quelled an uprising by the brotherhood in the town of Hama by killing an estimated 10,000 people.

“Like any other Muslim boy he was deeply affected by these events,” says his memoir.

When the Bosnian war opened a new front for jihadists in the early 1990s, Sakka left his job and headed for the conflict. He stayed in Turkey initially and established the “mujaheddin service office”, which provided medical support for Bosnia and later the two Chechen wars.

It soon became clear that more than medical help was needed. Sakka set up intensive physical training programmes in the Yalova mountain resort area, near Istanbul, to prepare the scores of young men heading for the conflicts. The memoir claims the volunteers came from Europe, Syria, Lebanon, Jordan, the Gulf, North Africa and South America.

The Chechens needed trained fighters. Sakka was telephoned by Ibn al-Khattab, the late militia leader controlling the foreign fighters against the Russians. Khattab requested that Sakka’s trainees should be sent on to Afghanistan for military training because “conditions are tough”.

This brought Sakka into contact with Abu Zubaydah, a high-ranking Al-Qaeda member, who ran a large terrorist training camp near the border between Afghanistan and Pakistan. Sakka was later to be sentenced in ab-sentia for involvement in the foiled Jordanian millennium bomb attacks in 2000 along with Zubaydah.

One of Sakka’s chief roles was to organise passports and visas for the volunteers to make their way to Afghanistan through Pakistan. His ability to keep providing high-quality forged papers made Turkey a main hub for Al-Qaeda movements, his lawyer says. The young men came to Turkey pretending to be on holiday and Sakka’s false papers allowed them to “disappear” overseas.

Turkish intelligence were aware of unusual militant Islamic activity in the Yalova mountains, where Sakka had set up his camps. But they posed no threat to Turkey at the time.

But a bigger plot was developing. In late 1999, Karahan says,a group of four young Saudi students went to Turkey to prepare for fighting in Chechnya. “They wanted to be good Muslims and join the jihad during their holidays,” he said.

They had begun a path that was to end with the September 11 attacks on America in 2001. They were: Ahmed and Hamza al-Ghamdi who hijacked the plane that crashed into the south tower of the World Trade Center; their companion Saeed al-Ghamdi whose plane crashed in a Pennsylvanian field; and Nawaf al-Hazmi who died in the Pentagon crash.

They undertook Sakka’s physical training programme in the mountains and later were joined by two of the other would-be hijackers: Majed Moqed, who also perished in the Pentagon crash, and Satam al-Suqami, who was in the first plane that hit the north tower.

Moqed and Suqami had been hand-picked by Al-Qaeda leaders in Saudi Arabia specifically for the twin towers operation, Sakka says, and were en route to Afghanistan. Sakka persuaded the other four to go to Afghanistan after plans to travel to Chechnya were aborted because of problems crossing the border. “Sakka [told Zubaydah] he liked the four men and recommended them,” said Karahan.

Before leaving, all six received intensive training together, forming a cell led by Suqami, which was similar to the Hamburg group run by Mohammed Atta, another ringleader in the 9/11 attacks.

At one point, Sakka claims the entire group were arrested by police in Yalova after their presence raised suspicions. They were interrogated for a day but eventually released because there was no evidence of wrongdoing.

Some of Sakka’s account is corroborated by the US government’s 9/11 Commission. It

found evidence that four of the hijackers – whom Sakka says he trained – had initially intended to go to Chechnya from Turkey but the border into Georgia was closed. Sakka had prepared fake visas for the group’s travel to Pakistan and arranged their flights from Istanbul’s Ataturk airport. The group of four went to the al-Farouq camp near Kandahar and the other two to Khaldan, near Kabul, an elite camp for Al-Qaeda fighters.

When Moqed and Suqami returned to Turkey, Sakka employed his skills as a forger to scrub out the Pakistani visa stamps from their passports. This would help the Arab men enter the United States without attracting suspicion that they had been to a training camp.

Sakka’s lawyer said: “Just like there is money laundering, there is also terrorist laundering and Turkey was the centre of this.”

According to Sakka, Nawaf al-Hazmi was a veteran operative who went on to pilot the plane that hit the Pentagon. Although this is at odds with the official account, which says the plane was flown by another hijacker, it is plausible and might answer one of the mysteries of 9/11.

The Pentagon plane performed a complex spiral dive into its target. Yet the pilot attributed with flying the plane “could not fly at all” according to his flight instructors in America. Hazmi, on the other hand, had mixed reviews from his instructors but they did remark on how “adept” he was on his first flight.

Paul Thompson, author and 9/11 researcher, said Sakka’s account was credible. “I think there is a lot more about the history of the hijackers that needs to be found out and Sakka’s claim may resume the debate about just how much was known about them before 9/11,” he said.

Sakka’s mountain trainees, meanwhile, had spread out to a number of countries where they carried out terrorist attacks. He claims this is why he was charged with a string of crimes committed by his associates. He was given a 15-year sentence in Jordan for the millennium bomb attacks, the death penalty for an an assassination attempt on Syria’s military intelligence chief and has been charged in Saudi Arabia for an explosives plot.

In effect, he had become a free-lance operative aiding a series of groups without necessarily agreeing with their targets. His links with Al-Qaeda, however, remained strong after the 9/11 attacks.

His lawyer says the Al-Qaeda leadership valued a number of his skills. “But most important,” he added, “was that Sakka was incredibly secretive. Al-Qaeda tested him many times, but he never once revealed a secret.”

The US invasion of Afghani-stan in late 2001 threw many of the Al-Qaeda camps into disarray. Many of the group’s fighters are thought to have fled across the border to seek safety in Iran.

According to Sakka’s account, one of those fighters was Zar-qawi. The precise movements of the Jordanian, who is thought to have been wounded fighting alongside the Taliban in Afghani-stan, have always been a matter of speculation.

Sakka’s initial role in the insurgency was to help foreign fighters enter Iraq. He took his family to live in Falluja, which was emerging as the hub of the foreign fighters’ resistance to the occupying forces.

He later told a court: “We held out for 70 days. They destroyed vast quarters of the city. It wouldn’t have been possible for them to enter before doing so. We ran out of ammunition and had to pull out.”

A month before the fall of Falluja, Sakka claims that he was part of the group that killed Kenneth Bigley, the British hostage. He describes himself as the “diplomat” who negotiated on behalf of the insurgents and says he presided over the court that resolved to execute him. He says Bigley’s body is buried in Falluja with his passport and confession video.

Today Sakka remains a controversial figure. The British Foreign Office says it has interviewed Sakka in jail about the Bigley murder. He provided a map of where Bigley was buried but the Foreign Office says they could not find the body. In Turkey, police sources claim Sakka may have become clinically insane or perhaps be an egoma-niac who has overstated his role.

The Sunday Times has spoken to a number of Al-Qaeda experts who say that many elements of his story ring true, but they are impossible to verify conclusively. Evan Kohlmann, an investigator for the 9/11 Finding Answers Foundation, said: “When [Sakka] was in Falluja there were several high-ranking Turkish guys there. It is also true that for a number of conflicts that Al-Qaeda has been involved in, Turkey is a very important through stop and a lot of fighters have travelled through there with the assistance of local people.”

Swift justice

Gordon Brown’s plans to double the detention period for terror suspects face further opposition with a report showing that America needs just 48 hours to file charges in Al-Qaeda cases.

The report by Justice, the human rights group, will say this week that Brown’s plans to extend precharge detention to 56 days are untenable.

It says: “No western democracy faces a greater threat of terrorism than the US. Despite this, the proven ability of US law enforcement to charge suspects in complex terror plots within 48 hours of arrest without resort to exceptional measures shows that UK proposals to extend precharge detention are both unjustified and unnecessary.”

The report emphasises the importance of FBI phone tap evidence and Brown is considering whether such intercept evidence should be allowed in Britain.

Eric Metcalfe, the Justice report’s author, said: “From Guantanamo Bay to rendition to torture, the US has done a lot of things badly wrong in the fight against terrorism.

“But in the rush to extend precharge detention here in the UK, we sometimes overlook what they are doing right.”

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