Edited for details: Unconfirmed reports suggested that most of the explosives used in the attempted attacks were triacetonetriperoxide - TACP - the same substance thought to have been used in the 7/7 attacks and was said to have been recovered from a suspected bomb factory in Leeds. TACP is known to degrade over time, which may explain why none of yesterday's devices exploded after the detonators were activated. Sir Ian Blair, the Metropolitan police commissioner, said some of the devices remained unexploded and that attempts had been made to set them off.
An explosives expert, Andy Oppenheimer of Jane's Information Group, said the small blasts could have been down to the bombs failing to explode properly or there being little explosive present. "It may be that there was a malfunction but it is not certain that there was substantial explosive in the devices. "This type of malfunction used to happen to the IRA, who had expert bombmakers ... It could be bad workmanship or it could be a deliberate attempt to disrupt the city two weeks later."
An army bomb disposal expert told the Guardian it was very unlikely that four devices would malfunction in the same way at the same time. "It is possible for the detonator to come out and just explode. The chances of all four doing that are remote." | If one incompetent guy put together four identical bombs, odds are pretty good they might all fail. |
Homemade bombs typically use a small amount of high explosive to set off a larger quantity of less volatile material.
Witnesses reported seeing white powder after the blast on the Hackney Road bus. Acetone peroxide, linked to the July 7 attacks, can be used both as a detonator and to cause larger explosions. The compound, which looks like a white power, was used as a detonator by the attempted shoe bomber Richard Reid.
Hans Michels, an explosives expert at Imperial College London, said a batch of acetone peroxide would turn to vapour so quickly it would lose almost two-thirds of its mass over a couple of weeks unless stored properly. | So it has a short shelf life. That would explain a lot. |
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