It's the sheer ordinariness of Mohammed Sidique Khan that has chilled his countrymen to the bone -- the 30-year-old primary school teacher, admired by his local community and happily married with a 14-month-old daughter, speaking in the homely flat vowels of his native Yorkshire.
But there was nothing ordinary about his words.
"I'm going to keep this short and to the point because it's all been said before by far more eloquent people than me. And our words have no impact on you," Khan said. "Therefore, I'm going to talk to you in a language that you understand. Our words are dead until we give them life with our blood."
It's not known when or where the recording was made, but on 7 July, Khan gave full meaning to those words when he blew himself up on a packed train at London's Edgware Road underground station. The explosion killed six people and injured another 120.
In the video, wearing a dark-green hooded top and a red-and-white headscarf, Khan left no doubt that he regarded all British citizens as legitimate targets.
"Your democratically elected governments continuously perpetuate atrocities against my people all over the world," Khan said. "And your support of them makes you directly responsible, just as I am directly responsible for protecting and avenging my Muslim brothers and sisters."
There could be no compromise, he said.
"Until we feel security, you will be our targets," Khan said. "And until you stop the bombing, gassing, imprisonment, and torture of my people, we will not stop this fight. We are at war and I am a soldier. Now you too will taste the reality of this situation."
But Muslim groups in Britain and the families and friends of the victims of the bombings have expressed outrage at the video. British Foreign Secretary Jack Straw rejected any linkage between the bombings and the war in Iraq.
"We're waiting for police assessments of the video which, of course, I have seen," Straw said. "But I also say this -- there is no excuse, no justification, for terrorism of any kind. And it happens that those who entirely wrongly claim to speak in the name of Islam are mainly killing their fellow Muslims."
The tape strengthens the argument that the 7 July bombings were linked to Al-Qaeda. Khan singles out Osama bin Laden and his deputy Ayman al-Zawahri for praise at the end of the recording, as well as Abu Mus'ab al-Zarqawi, the Al-Qaeda-linked militant behind many of the insurgent activities in Iraq.
The link is made even stronger by the appearance on the same videotape of a separate recording of al-Zawahiri, in which he said that the London bombings were proof that Al-Qaeda has moved the battle to what he called the "enemies' land."
The London bombings, he said, had been a slap to the face of British crusader arrogance. And he singled out Jack Straw for particular scorn.
"Didn't the lion of Islam, the Mujahid Shaykh Osama bin Laden, may Allah protect him, offer you a truce so that you might depart from the Islamic lands?" al-Zawahri said. "But you were obstinate and were led by arrogance to more crime and your foreign secretary, Jack Straw, said these proposals deserve to be met with contempt."
British intelligence, though, is not yet fully convinced of a link between Al-Qaeda and the London bombers. Certainly, the Al-Jazeera recordings demonstrate that the London bombers were inspired by Al-Qaeda, but do not prove that they were acting under its command.
Al-Qaeda's leadership structure has been badly damaged since 9/11, with bin Laden forced into hiding, and the video message may just be an opportunistic attempt to burnish its reputation and show that it is still the guiding force of jihadist opposition to the West.
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