Cheap, crude and made to murder

NAIL BOMBS

Weapons experts said these devices were a departure from the tactics used by the bombers so far.

Such weapons are easy and cheap to make and are designed to "tear into flesh" and cause death.

The nail bomb has explosives packed into a milk bottle wrapped with nails and shards of metal.

The devices appeared to have fuses protruding from the top but they were unprimed and it is unclear whether the fuse would have been used as a detonator.

Usually, they are thrown into a crowd, with the range a circumference of about 10m.

Robert Ayers, an explosives specialist with 30 years' experience with the United States Army and the CIA, said: "These are anti-personnel weapons, like a home-made grenade, and the effect would be to tear through flesh causing terrible, lethal injuries.

"An explosive charge or fuse would be used for the detonation. If the bomber wanted to die, he could detonate with a switch."

Explosives specialist Andy Oppenheimer said: "These are the simple and horrible type of bomb which have been used to deadly effect by gangs in Northern Ireland and [the Palestinian territories]."'

CIRCULAR BOMBS

These devices, around 13cm in diameter and around 2cm thick, were packed parcels of explosives, tightly wrapped in clingfilm. These were likely to have been the type of bombs used in the July 7 attacks.

The bombs would have been carried in rucksacks, and possibly within containers to make a larger device which would have a devastating impact.

The base explosive is believed to be homemade acetone peroxide - also known as "Mother of Satan" - perhaps mixed with a military explosive to enhance the blast.

"One could put in as many as the rucksacks would allow," Ayers said.

Oppenheimer said the bombs, in the state they had been discovered, were incomplete.

"These are unfinished bombs waiting to have detonators attached.

"I believe there was a mixture of explosives because of the destructive effect that we can see in the pictures of the damage to the Piccadilly line train."

- INDEPENDENT