Terrorist video made in Pakistan...

Definitive proof that Al-Qaeda was behind the attack in London.

The chilling video message of Mohammad Sidique Khan, the British suicide bomber, was recorded in Pakistan after he was given orders to attack London, MI5 investigators suspect.

According to senior Whitehall officials, the Security Service is probing the theory that Khan, 30, was filmed during a three-month visit to Pakistan with fellow bomber Shehzad Tanweer, which began in November last year.

British investigators are working with security services in Pakistan to try to identify where the video was recorded - possibly Rawalpindi, a hotbed of terrorism close to Islamabad.

The video was broadcast last Thursday by al-Jazeera, the Arabic television station. Khan, in his native Yorkshire accent, said: "We are at war and I am a solider." He blamed Britain's involvement in Iraq for his intended suicide mission.

In part of the video not yet given to al-Jazeera Khan is reported to have been filmed with Tanweer, 22, the second member of the July 7 suicide team that killed 52 other people and injured more than 400. Al-Qaeda often staggers the release of video footage to gain maximum publicity.