In the summer of 2006, as they were making final preparations for the plot to bring down multiple airliners over the Atlantic, both Abdulla Ahmed Ali and Assad Sarwar took time out to send e-mails to Pakistan.
They were communicating with Rashid Rauf, a British man from Birmingham who had been living in Pakistan for six years.
Their e-mails, written in code, were essentially updates on their progress.
“I set up my music shop now. I only need to sort out an opening time. I need stock … Ali wrote on 3 August 2006.
The prosecution said he was telling Rauf that the bomb factory was ready, that he just needed to choose a day for the attacks and to get hydrogen peroxide, a key ingredient, from Sarwar.
So who is Rashid Rauf? Why were the plotters communicating with him about their plans?
British officials believe he was their link with al-Qaeda, possibly involved in their training.
Recent intelligence assessments suggest his involvement in plans to attack Britain go back several years.
At the end of 2008, MI5 and MI6 wrote to Parliament’s Intelligence and Security Committee to say that “in the light of recent analysis of intelligence received” Rauf may have been involved in the 7 July London bombings.
They said their assessment was that he was a “facilitator” of the attacks, and that the bombers were “directed some way by elements of al-Qaeda based overseas”.
Rauf also has links to Muktar Ibrahim, the leader of the failed 21 July London bombings.
When Rauf’s house was raided in 2006, Pakistan police found the belongings of two British men who had travelled with Ibrahim to Pakistan in 2004 - and then disappeared.
Information about Rauf has continued to come in, most notably from men detained in the United States and Belgium.
There were even arrests in Britain this year because of intelligence about Rauf’s future plans, though in the end nobody was charged.
Rauf first came to the attention of police in the late 1990s when he was accused of obtaining a satellite phone by deception.
In 2002 he fled Britain after his uncle was savagely stabbed to death in Birmingham, and intelligence suggests he spent the subsequent years in Pakistan, plotting attacks on the West.
He was eventually arrested in 2006, but at exactly the wrong moment.
On 9 August Scotland Yard’s Counter Terrorism Command had what they say was “good coverage” of the suspects in the airline plot.
They were following the leaders and keeping track of the movements of the others. They just wanted more definitive evidence before they moved in.
Then came news that Rauf had been detained in Pakistan and, to their intense annoyance, British detectives had to bring the whole operation forward in a hurry.
A senior police officer has told the BBC that Rauf’s arrest followed a meeting at the White House, chaired by President George W Bush himself.
he president and his advisers were so concerned about the risk to America that they encouraged the Pakistanis to take Rauf into custody. This has been denied by former advisers to President Bush.
When asked about it, a British official said: “We know that when we share intelligence with our partners, they will sometimes make different decisions on grounds of their own national security.”
The story does not end there. Rauf’s lawyers claim he was tortured in Pakistan and the next year he made an extraordinary escape.
Two police officers were accompanying him back from court when, bizarrely, they let him enter a mosque unguarded to pray, and he simply disappeared.
Last November came news that he had been killed in Pakistan by a missile fired by a US drone. But his body has never been recovered.
The British intelligence assessment is that Rauf - a key figure in the 7 July attacks and the airline liquid bomb plot and possibly many others - is more likely dead than not.