THE adapted jacket being sought by anti-terrorist officers after the raid yesterday was almost certainly intended as a suicide weapon, even if the explosives it contains are not sufficiently powerful to kill.

The garment, which was likened by security sources to a photographer’s jacket or waistcoat, is said to have carried an explosive charge that would be used to release a poisonous chemical in a confined space.

Assuming that the device was to have been triggered by the wearer rather than remotely, the bomber would have stood little chance of escaping himself, explosives experts said.

The use of a charge to spread a chemical weapon, however, is somewhat puzzling, as there are less technologically sophisticated methods of releasing many toxic agents that would be less likely to fail.

A bag containing a volatile liquid or gas could simply be punctured, releasing toxic vapours. An explosive charge might also destroy some of the device’s lethal payload.

Professor Hans Michels, of Imperial College, London, said the explosive approach suggests three design possibilities.

If the chemical was enclosed in a pressurised container, similar to an aerosol can, then bursting or piercing it would have the effect of causing a small explosion and scattering its contents over a wide area. Such a device could easily be concealed in a thick jacket, he said.

A second possibility is that the agent is in the form of a powder, which would require a small explosive blast to release it. In an enclosed space, such as a train carriage or a bar, it would be readily inhaled or, depending on the chemical used, it could poison people through contact with the skin.

It is also possible that the device relied on a reaction between two chemicals which, when mixed, would produce a toxic gas such as chlorine. The explosion would ensure that the agents mixed with one another, as well as supplying energy that might be needed to start a reaction.

“You would have to assume that the bomber would not be planning on escape with a device like this,” Professor Michels said. “If you use an explosive charge to release something, the person who detonates it is always going to be the first sufferer, so it would be a suicide weapon.”

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