Watch the video: Osama Bin Laden's HQ

Two bearded young men laugh and joke for the camera. They appear relaxed, well groomed, intelligent; they might be high-achieving students quietly celebrating an exam success. They look at a piece of paper and laugh some more.

What is so funny? Certainly not the piece of paper. There is Arabic script on it. Easily decipherable is the word “al wasiyyah”. This means “the will”.

It is the handwritten last testament of Ziad Jarrah, the lighter-haired and better-looking of the two young men. A well educated, middle-class Lebanese, he has been studying in Germany. So has his dark-haired companion, Mohammed Atta, also middle class and university educated, but born in Egypt. Atta has his will, too. Unsmiling, both men read them to camera.

These images are part of a videotape, nearly an hour long, that was filmed at Osama Bin Laden’s lair in Afghanistan 6½ years ago. They are revealed today for the first time, and they are a missing chapter in the searing story of the attacks on America on September 11, 2001.

Atta led the team of 19 suicide attackers and flew American Airlines flight 11 into the north tower of the World Trade Center. Jarrah piloted United Airlines flight 93. His assigned target was Capitol Hill, but the plane crashed.

ATTA and Jarrah have never been pictured together before. Indeed, a key element of their tradecraft was that they steered clear of each other. They were leading figures in the September 11 story, not only because they flew the planes but also because they apparently had everything to live for. Unlike most of the other hijackers, who were mainly provincial Saudi fundamentalists, Atta and Jarrah fitted easily into western society.

To the Germans who knew them in Hamburg they seemed entirely normal. The tape explains this mistake. It would be hard to look less homicidal — until the camera pulls back and reveals that Atta is sitting next to an AK-47.

So the tape not only fills a gap in the story of September 11 but also provides chilling proof of the difficulty of fighting Islamic terrorism: these two “normal”, happy, unthreatening individuals turned out to have an explosive effect on the history of the 21st century.

The unedited video was passed to The Sunday Times through a previously tested channel. On condition of anonymity, sources from both Al-Qaeda and the United States have confirmed its authenticity. It has no sound — and lip-readers have failed to decipher it, according to a US source — but the images speak loudly for themselves.

The tape not only features Atta and Jarrah. It also gives a rare and intriguing sight of Bin Laden with his inner court.

It opens with 100 or so Al-Qaeda hardcore members sitting on the ground in the open air, obviously expecting something to happen. Among them are several children.

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