Just how close were the three Britons, found guilty on Monday of plotting to kill thousands by blowing up transatlantic airliners, to putting their deadly plan into action?
Two of the men were waiting for new passports, no viable bomb or explosives had been made, no tickets had been bought and there was little to indicate that an attack was imminent.
But intelligence that one of the men would attempt to bypass security and board a plane with the components for a bomb forced detectives to act, perhaps sooner than they would have liked.
The lack of evidence against four other men accused of being would-be suicide bombers meant they were cleared by a jury in London of planning to blow up planes.
But British police, who carried out the biggest surveillance operation in their history requiring the back-up support of 220 officers from all over the country, are in no doubt the plotters were ready to strike. "We believe they were within days," a senior police source said.
"We believe that they were contemplating some sort of dummy run with one individual travelling towards the end of the week," adding the actual attacks to bring down airliners mid-flight would have taken place a week or so later.
PLOT NOT THAT ADVANCED?
Some commentators have suggested US security agencies put pressure on their British colleagues, and that the plot was not as advanced as the authorities and politicians have claimed.
"We were reviewing and re-reviewing on a daily basis. It was a fine balancing act to run it as far as we did," the senior police source said, dismissing the suggestion they were forced into the arrests. They moved as "it was too risky" not to.
When they did pounce in August 2006, chaos at airports followed. More than 1,000 flights were cancelled in Britain at the height of the holiday season and passengers were initially banned from taking luggage on board aircraft.
It also led to lasting restrictions on carrying liquids on flights. This was not an over-reaction, police say.
"We are entirely satisfied they were viable devices," the source said. "Certainly (Assad) Sarwar (one of the suspected ringleaders) indicated he felt these were viable devices."
At Sarwar's home in High Wycombe, 35 miles west of London, and buried in woodland nearby, detectives found the ingredients for the primary charge -- HMTD, and dozens of bottles of hydrogen peroxide -- the main base of the explosives.
The jury were shown the effect of exploding a mocked-up bomb in a 500 ml drink bottle. It shattered protective glass and blew surrounding panels off the wall.
Security and aviation analyst Chris Yates said it would have been quite possible for the men to have made the HMTD and explosives, and to have put together the bombs from the components on board a flight.
But he said, as HMTD compound is very unstable, there would always be a risk that it would self-ignite as the men transported it or placed their bags in overhead lockers.
"There are a bunch of questions as to whether it could actually have been carried out with any degree of success," he told Reuters.
"Did we jump the gun on this? I think yes we did. There's a general feeling within many in this industry that that plot, while theoretically possible, may not have been as robust as portrayed."
The 2006 plot was not the first one to involve liquid explosives. The 1995 "Bojinka plot", hatched by Ramzi Ahmed Yousef, jailed for plotting the 1993 World Trade Center bombing, aimed to down 12 US-bound airliners with liquid explosives.
A Japanese passenger was killed during a test run when Yousef placed a bomb under his seat on a Philippine Airlines flight from Manila in Dec. 1994.
But the plot was uncovered when a fire broke out at a Manila apartment where Yousef was mixing chemicals. However British police said the 2006 plot was still unique.
"I don't think we had seen anything like it before. It was specific to this plot," the source said, adding there was no reason "to suppose it wouldn't have got through".