Terror connection suggests the attackers had explosives training

On 4 August, Osama Bin Laden's lieutenant Ayman al-Zawahri warned in a videotape broadcast on Arab satellite channel al-Jazeera that London will face more attacks because of Prime Minister Tony Blair's foreign policy.

But there was always the assumption that Britain's suicide bombers were somehow amateurish - Hussain was apparently totally thrown by disruptions on the Northern Line, leading him to panic and jump on to the No 30 bus.

Reports of amateur substances used in bombs, released by New York Police rather than Scotland Yard, added to this belief.

The surprise of colleagues of Mohammad Sidique Khan added to this impression. Married with a very young daughter, he had been a teaching assistant at Hillside Primary School in Leeds since 2002.

Parents at the school said the young pupils' "mentor" was highly regarded by both children and parents. On 18 July, Pakistani officials confirmed that three of the four London suicide bombers had visited Pakistan last year.

Khan and Shehzad Tanweer arrived and left together, and spent three months there. Hasib Hussain, one of the perpetrators of the subsequent failed suicide bombings on 21 July, flew in last July for an unknown period, where they are believed to have been trained, or "brainwashed" by al-Qa'ida.