A man charged with drawing up plans to carry out coordinated terror attacks in Manchester, New York and Copenhagen is due to go on trial today in the US.
Abid Naseer is accused of being the ringleader of the UK-based conspiracy, which experts say had the potential to be "second only to 9/11" in its impact, with an estimated death toll higher than the 7/7 bombings.
The UK target is believed to have been the Arndale shopping centre, or in the vicinity of St Ann's Square in Manchester.
A former FBI agent who worked on the hunt for Osama Bin Laden, Manny Gomez, described the potential damage by the plots as "devastating".
"The impact, the terror that this would have created in these particular cities would have been devastating to those cities' economies, to just the mindset of these people carrying on day to day," he said.
"It would have been huge, it would have been only second to 9/11 in terms of death, damage, devastation to the psyche of the people being affected by it, it would have been significant."
Over the past five years, six men have been found guilty of their part in the New York and Copenhagen plots, and prosecutors are likely to argue that Naseer used widely-recognised al Qaeda code in his communications.
This includes using weddings and girls' names when referring to dates and targets.
Naseer, a Pakistani national in the UK on a student visa, was first arrested in 2009 as part of an anti-terror operation in the northwest of England.
But, after the Met's Assistant Commissioner Bob Quick was photographed carrying clearly-visible details of the investigation, the operation was deemed to be compromised and Naseer, along with nine others, was released without charge.
Despite a ruling by the Special Immigration Appeals Commission that he constituted a serious threat to national security, Naseer won his appeal against being deported because he was at risk of being tortured or killed back home in Pakistan.
He was then rearrested in July 2010, when the US requested his extradition to face charges of supporting a foreign terrorist organisation and conspiracy to use a destructive device.
He was extradited in January 2013, and has been in custody awaiting trial since.
Naseer denies the charges made against him.
Timeline of the three plots
April - UK: Operation Pathway is brought forward after the Met’s Asst Commissioner Bob Quick was photographed with papers detailing the Operation going into Downing Street.
After a press blackout, hundreds of police raid 10 properties across the northwest of England and make a number of arrests, including 10 Pakistani nationals on student visas (one of whom was Abid Naseer).
All the men were released without charge two weeks later.
September - New York: Najibullah Zazi arrested and charged with conspiracy to use weapons of mass destruction in relation to a planned plot to blow up NYC subway.
January - New York: Adis Medunjanin and Zarein Ahmedzay are arrested in NYC on similar charges.
February - New York: Najibullah Zazi pleaded guilty to the subway plot conspiring to use weapons of mass destruction (explosive bomb), conspiracy to commit murder in a foreign country, and providing material support to a terrorist organisation.
April - New York: Zarein Ahmedzay, 25, pleaded guilty to same charges for his role in an al Qaeda plot to conduct coordinated suicide bombings on New York's subway system.
May: UK. Abid Naseer wins his appeal against extradition to Pakistan on basis he would face torture if he returned home.
July - UK: Abid Naseer is re-arrested after the US requested his extradition on charges of supporting a foreign terrorist organisation and conspiracy to use a destructive device.
The Department of Justice said he was one of five people accused of participating in two plots in New York City and Manchester.
July - Norway: Three men arrested in Norway and Germany on suspicion of carrying out an attack on Danish newspaper Jyllands-Posten in Copenhagen.
May - Pakistan: Bin Laden’s compound in Abbottabad is raided, leading to discovery of materials showing links to the three plots.
January - Norway: Three men were found guilty of involvement in an al Qaeda plot to attack a Danish newspaper that caricatured the Prophet Muhammad, the first convictions under Norway's anti-terror laws.
May - New York: Adis Medunjanin is found guilty of conspiracy to use weapons of mass destruction and other terrorism charges.
Najibullah Zazi and Zarein Ahmedzay were the first admitted homegrown terrorists to give evidence in a US court as they testified against Medunjanin.
January - UK: Abid Naseer loses his fight against extradition and is moved to US to face terrorism charges.
February - New York: Abid Naseer to face trial in New York City.