Robert Ayers, a security analyst at Chatham House in London, said that that he believed that the same group was behind both attacks. “All along I’ve been saying that you had four guys that died [in the July 7 bombings], but the infrastructure that trained them, equipped them, funded them, pointed them at the right target - the infrastructure’s still in place, still here,” he told the Reuters news agency.
But if the same group was involved, the obvious question was why the first wave of attacks was so professional and deadly, and second was apparently so amateur, continued Mr Ayers, a former US intelligence official. “One speculation I’ve had all along is that they left those explosives in the car for another group to pick up and carry out a second attack, but when they got there the car had already been taken over by the police, so they have had to cobble something together fairly quickly,” he said. “From what I’ve been able to gather, either the bombs themselves are very, very small compared to two weeks ago, or they’ve got a manufacturing problem and only the detonators are going off, and not the primary charge. They’re certainly using explosives that aren’t nearly as powerful.”
Experts agreed that there were two explanations for today’s attack. The first, more benign, is that the attacks were carried out by “imitative amateurs” inspired by the July 7 blasts. The second, more worrying, was that the same group behind the suspected al-Qaeda linked attackers had struck again. Michael Clarke, a security expert at King’s College London, told Reuters, said: “The more we know about the bomb attack two weeks ago, the more skilful it looks, well planned - the people behind it know what they’re doing.”
Professor David Capitanchik, a terrorism expert based at Robert Gordon University in Aberdeen, warned that today’s explosions may have been “amateurish” devices deliberately aimed at emergency services who arrive at the scene. He said eyewitness reports of small explosions in a rucksack could indicate that they were not intended to explode properly until they had been recovered. “It appears as if the detonators have gone off, but reports indicate a much more amateurish-made device than the bombs two weeks ago,” he said.