text: As Abid Naseer started his cross-examination in a New York courtroom of the police officer who searched his Manchester bedroom in 2009, he commented it was nice to hear a Mancunian accent again.
  Six years ago, the Pakistani national had been living in the north-west English city where he plotted to kill hundreds in a bombing attack at the city centre's Arndale shopping complex during Easter weekend.
  Naseer, who was extradited from the UK to the United States in 2013, was convicted of providing and conspiring to provide material support to al-Qaeda and conspiring to use a destructive device.
  Defending himself at his trial in New York, the 28-year-old was polite, calm and professional. He denied he was involved in any form of extremism.
  But, according to the police officer who headed up the British investigation into his activities, his courtroom conduct was a performance designed to con the jury.
  In a cafe overlooking the Brooklyn courthouse where the trial was held, Det Supt Mark Smith said Naseer was a good actor, an al-Qaeda trained terrorist and a man with a determination to kill hundreds of people.
  He said: "He has had lots of time to develop his Westernised social skills, but I would say don't be fooled. Beneath that cool, relaxed exterior is a cold, calculated terrorist."
  Held in custody in the US ahead of his trial, Naseer had spent the months preparing his legal case and working out.
  One police officer commented that he had doubled in size since he was handcuffed and led away from a Cheetham Hill house in April 2009.
  Were it not for his arrest, detectives are convinced he would have gone ahead with a "mass-casualty" attack in Manchester city centre.
  Based upon intelligence gathered and the plots devised by other terrorists trained at the same al-Qaeda camp in Pakistan, police have pieced together what they believe would have happened.
  Emails sent from an internet cafÃ© near Naseer's home had been intercepted in the weeks before his arrest. The final message led police to believe an attack was imminent.
  Known as the "Hi Buddy" email because of the way it greeted an al-Qaeda operative, it reads: "I met with Nadia family and we both parties have agreed to conduct the nikah after the 15th and before 20th of this month. I have confirmed the dates from them and they said you should be ready between these dates."
  The jury was told female names, including Nadia, represented different ingredients used to make bombs. Wedding, or 'nikah', was a standard al-Qaeda code for a terror attack.
  Based on the Islamic calendar, investigators believed this email was referring to a planned attack during the Easter weekend in 2009.
  Other evidence included photos of Naseer's friends standing in front of the main entrances to the Arndale centre.
  He claimed they were innocent pictures as they travelled around Manchester. But retired Det Ch Insp Allan Donoghue described the images as "hostile reconnaissance".
  He said: "That for me was the most alarming thing. To see each entrance of the Arndale Centre being photographedâ€¦ that was clearly a means by which they would brief the would-be attackers as to what they would see as they made their approaches."
  Police think the first target would have been the Arndale Centre, which had been rebuilt following the IRA bomb attack on Manchester in 1996.
  The terrorists would have walked in carrying bombs made out of fizzy drink bottles in rucksacks or specially modified T-shirts.
  After the first wave of explosions, there would have been a second attack with more suicide bombers waiting in St Anne's Square for the rush of shoppers trying to escape.
  The target was chosen by al-Qaeda leaders because of the financial impact as well as the huge number of potential victims.
  According to Dr David Lowe, a retired special branch officer who now teaches law at John Moores University in Liverpool, it would have been a devastating attack.
  He said: "It would have potentially been bigger than the 7/7 attack in London. It would have sent shockwaves around the world. And it would have shown that not just capital cities are targets."
  The scale of the potential disaster is something the man who led the police investigation is well aware of.
  Det Supt Smith said the relief he felt at the time of the arrests continued today.
  "Every day since that time I've thought about this case and wondered exactly what would have happened if we didn't detain him.
  "I've always been convinced that we prevented an atrocity in Manchester."
target: Pakistani national Abid Naseer was convicted of plotting attacks in several countries after being extradited to the US from the UK, where police believe they averted an "atrocity" by his detention.