It was supposedly the biggest terrorist plot since 9/11, a grotesque plan to blow up seven transatlantic planes simultaneously that would have killed more than 1,000 people had it not been foiled two years ago.
But an inconclusive verdict in the British trial of seven alleged perpetrators has raised fresh questions about the plot, the police operation that unraveled it, and the international counterterrorism collaboration so vital to defeating extremists.
After a five-month trial, the jury decided Monday that three of the seven accused – Abdulla Ahmed Ali, Assad Sarwar, and Tanvir Hussain – had indeed been plotting to kill using a form of hydrogen peroxide liquid bomb disguised as a soft drink. But the jury could not decide whether aircraft were the target. They also decided that four other defendants were not guilty. Prosecutors are considering a retrial.
Terrorism experts say the verdict was a setback to British counterterrorism efforts, which have notched up a volley of successes over the past three years.
Operation Overt, as it was known, was the biggest counterterrorism investigation in British history, costing around $60 million since the day in May 2006 when Britain's MI5 intelligence agency began focusing on Mr. Ali. The day of the arrests three months later brought mayhem to international aviation; security measures introduced involving a ban on soft drinks in hand luggage persist to this day.
"What seems to have been the trigger was the demand by the US for the arrest of one associate [in Pakistan] and a concern that perhaps the plotters would see the arrest of colleagues and stand down the operation," says Bob Ayers, an analyst at London's Chatham House think tank.
Peter Clarke, the former British counterterrorism chief who led Operation Overt, said that the arrest of Mr. Rauf gave officers a real problem. "On the evening of Aug. 9, 2006, I was told that a man connected to the British terrorists had been arrested in Pakistan," he wrote in the Times. "This was not good news. We were at a critical point in building our case against them. If they got to hear that he had been arrested they might destroy evidence and scatter to the four winds. More worrying still, if they were tipped off to the arrest they might panic and mount a desperate attack."
The revelations lay bare the crucial dilemma at the heart of any counterterrorism operation – whether to allow plots to mature so as to build up valuable evidence, or whether to move early to protect the public.
"The authorities here like to wait close to the last minute, wait until the plotters have incriminated themselves enough so that the evidence can stand the test of a trial," says Sajjan Gohel, a security analyst with the London-based Asia Pacific Foundation think-tank.
"The US, however, wants you to act early in case plotters disappear off the radar," Mr. Gohel says. "There have been cases of people who were monitored but disappeared and carried out attacks at a later date." A prime example: the July 7, 2005, London bombings ringleader Mohammed Sidique Khan.
Despite the setback, the trial underscores two important things about Britain's battle with home-grown terrorism.
First, it makes further connections between the various terror cells that have been pinpointed in recent years. Cellphone records show a link between the trio convicted on Monday and the July 21 bombers. Both groups – and the July 7 bombers – planned attacks using hydrogen peroxide-based bombs. Members of the so-called airline cell, the July 7 cell, and cell convicted last year spent months in Pakistan, some at the same time.
Second, it suggests that the security services are at last getting to grips with their new adversary. Not one plot since July 7 has been carried out (apart from a pyrrhic attack on Glasgow airport in 2007). Several plots have been thwarted and dozens of convictions obtained.
But with 2,000 extremists considered dangerous still at large and perhaps 30 plots still active, counterterrorism officials have their work cut out for them.