Defiant message from bomber was filmed on British soil, claim security services

Officials carrying out forensic analysis of the tape showing Mohammed Sidique Khan believe that it was probably produced about seven months ago. Khan's image on the video is said to be similar to photographs of him taken during that period, which are now in the possession of the police.

At that time, Khan had taken time off from his job, as a classroom assistant, because he was suffering from depression. During the same period he was in the process of splitting up from his wife who had complained his personality and lifestyle were changing.

Investigators believe that if the videotape was produced during a visit to Pakistan, Khan would most likely have been shown with military paraphernalia. Instead, he is shown in civilian clothing, holding nothing more than a ballpoint pen.

Security sources also say that Ayman al-Zawahiri, regarded as Osama bin Laden's deputy, who appears after Khan on the same tape, issued another video on 4 August warning the British people of more impending attacks. In this earlier videotape there was no reference to Khan and al-Zawahiri stopped short of claiming that the London bombings had been carried out by al-Qa'ida.

Investigators believe that the video of Khan was smuggled to Pakistan by associates of Khan and passed on to al-Qa'ida. Images of al-Zawahiri were then spliced on to the tape before its release to the al-Jazeera arabic television network.

Irshad Hussein, a friend of Khan, said yesterday that it showed him looking very different from the way he was just before the 7 July bombings. Mr Hussein said the tape could have been made as long as a year ago.

Khan, 30, who lived in Dewsbury, West Yorkshire, with his wife and 14-month-old daughter, killed himself and six civilians in the Edgware Road bomb and is believed to have been the leader of the 7 July terror cell.

In his video message, broadcast for the first time on Thursday night, Khan blamed the British public for the bombings, which claimed the lives of 52 innocent people. He said their support for the Western governments that "continuously perpetuate atrocities" against the Islamic world made them "directly responsible".

Khan also declared: "We are at war and I am a soldier." He also warned of further attacks.

Khan had visited Pakistan, and possibly Afghanistan, with another of the bombers, Shahzad Tanweer, last year. Police sources say they are "aware" of rumours that another video, made by Tanweer, is imminent.

The intelligence service is certain that the two men met Islamist militants at the time, but, they maintain, extensive inquiries since then had not yielded any evidence of direct al-Qa'ida involvement in the London bombings. Rather than being in charge of the London bombings, al-Qa'ida, the investigators believe, is now attempting to capitalise on them.

But the very fact that the tape was passed on to al-Qa'ida shows that Khan's associates have international connections.

Scotland Yard and MI5 are also re-examining links between Khan and an alleged plot in March 2004 to explode a bus packed with explosives. Eight men were arrested after the discovery of 600lb of ammonium nitrate fertiliser, a potential ingredient for bombs, in a lock-up garage. Details of the case cannot be publicised for legal reasons.

Khan was regarded as a peripheral figure in that investigation - his details were found on one of the arrested men - and he was not put under surveillance. Security sources accept that it was a mistake not to have put him under proper scrutiny and that this was a "failure of intelligence".