In April 2002, as chief investigative reporter on Al-Jazeera, I was taken blindfolded to meet Khalid Sheikh Mohammed at a safe house in Karachi.

He introduced himself as the head of Al-Qaeda’s military committee and admitted responsibility for 9/11. Altogether I spent 48 hours with KSM — as he is known to the intelligence community — and another key figure, Ramzi Binalshibh, whom he described as the 9/11 co-ordinator. Ramzi was captured in September 2002; KSM in March 2003.

Last week, during a secret hearing at Guantanamo Bay, KSM confessed to 31 separate plots. According to a transcript released by the US military, he claimed responsibility for the 1993 bombing of the World Trade Center, the Bali bomb, which killed 202 people, plots to kill Bill Clinton and Jimmy Carter and attacks on Big Ben, Heathrow and Canary Wharf in London. He boasted that he had beheaded Daniel Pearl, the American journalist. Most importantly, he said he planned the September 11 attacks “from A to Z”.

I was not surprised. In person he had struck me as shrewd and blunt. A doer, while Ramzi was a thinker. They’d decided to talk to me to mark the first anniversary of 9/11. They showed me a glossy Boeing brochure and manuals, a thick “how to fly” textbook, an air navigation map of the American eastern seaboard, books on how to speak English and flight simulator CD-roms. They gave me details that could be checked.

I think the real father of the 9/11 plot was Muhammed Atef, Osama Bin Laden’s security chief, who was killed in 2001. But it was KSM who made it happen by joining the well resourced Al-Qaeda to carry it out.

If Mohammed Atta, the Egyptian who led the 9/11 suicide team, hadn’t come to him I doubt that 9/11 would have happened. Before then KSM was dealing with the kind of guys who wanted to die but were not very skilful — good “muscle”, but he needed brains. That explains why 9/11 was a success and smaller operations were not. He did not have another Atta to pull them off.

I have no doubt that he would have liked to have been responsible for all the claims on the transcript, but was he? One thing that is missing, which I’m sure he was responsible for, is the Djerba operation in Tunisia: a tanker drove into a synagogue there in 2002, killing 21 people, after KSM gave the perpetrator his approval. That kind of “responsibility” is not uncommon. Maybe he forgot that one.

So he seems to be taking responsibility for some outrages he might not have perpetrated, while keeping quiet about ones that suggest his hand. I think he has blurred the line between what he did and what he was hoping or plotting to do.

He wants to take the credit for high-profile attacks because he is a pragmatist, a power-hungry mastermind, and realises his time is up; he might as well gain sympathy as an ideological hero.

He lived for this spotlight, the chance to say: “Look at this spectacular operation I pulled off against the most powerful nation on earth.” But he is not a fantasist. KSM is a guy who enjoys plotting and being in the field. He could be the head of the mafia and also the imam of a group of people praying in Afghanistan. He would enjoy both roles.

Another possibility is that he might be taking credit so other people, still at large, can avoid the blame. We can never know for sure. One thing that is clear is his wish to be dignified as a prisoner of war. When he mentions George Washington, he is addressing America. He is saying: “This is your own hero, you used to be oppressed by the Brits and the Brits considered George Washington to be a terrorist.”

He knows that the smallest count against him will be enough to have him executed. Hardly anyone, even in Al-Qaeda, will believe he was responsible for all these operations. But he’s hoping they’ll think he has been selfless.

He is not a man of Allah but a man of action. I knew that when they were captured it would be KSM who talked first. Ramzi would be much tougher to interrogate: a true believer in Allah, in his own way. I would bet when he was captured Ramzi thought: “My true jihad has just started.” KSM would have thought: “This is it, game over.”

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