A BBC investigation into the ringleader of the 7 July bombing gang has revealed details of how he turned to terrorism.
Video: Khan denounced West in recording
The Radio Four documentary about Mohammad Sidique Khan established he spent most of his life as a westernised youth who did not talk about religion.
While his path into terrorism had been linked to radical mosques, close friends reveal this was not the case.
They say he became part of a tight-knit group of young radicals who watched violent videos about Muslim suffering.
The documentary Biography Of A Bomber spoke to a former member of his inner circle who tells of violent Jihadi videos being played in an attempt to radicalise young men.
Mohammad Sidique Khan blew himself up on 7 July while travelling on the London Underground near to Edgware Road. He killed himself and six other people.
As the oldest of the four bombers, investigators assume he was the ringleader.
Earlier this week, new footage of him denouncing the West and criticising Muslim leaders emerged on the internet.
While Khan's path into terrorism has been blamed on radical mosques and a lack of integration into British society, the BBC investigation reveals that neither of these appeared to be factors in his radicalisation.
BBC reporter Nasreen Suleaman has uncovered close friends who say that his radicalisation happened in backrooms in Yorkshire, rather than in religious institutions or foreign trips.
In the documentary "Khalid", a former member of Khan's inner circle, says that Khan became part of a tight-knit group of young, radicalised Muslim men from Dewsbury, Leeds and Huddersfield.
Paintballing and videos
The men used to spend time paintballing, trips that would take place immediately after watching extremely violent videos depicting Muslim suffering around the world.
Another of the bombers, Germaine (or Jamal) Lindsay was also involved in this group, according to Khalid.
"Before we would leave the house, there would sometimes be a video reflecting what's happening in Palestine or Chechnya or other places where Muslims were affected," Khalid tells the documentary.
"Looking back on it now I do find it a bit weird that we had such a viewing. I can see why some youth would be affected by this - they get fired up, they get stirred up - and having the airing of that video might not have been in the best interests of certain people.
"Mohammad Sidique Khan was there but someone else was introducing the videos."
Khalid tells the BBC that Khan's well-documented final trip to Pakistan, and suspected visits to Afghanistan in the year before the bombing, were to link up with Jihadi fighters.
"I heard it frequently that he was going overseas for military training. I heard it from a very sound source.
"I don't know why he was prepared to let people know what he was doing - perhaps they were looking for other recruits or perhaps they just felt comfortable telling people."
Dreams of America
The documentary also reveals for the first time details of Khan's earlier life, including his apparent dream to become an American.
Khan as a teenager shook off his Pakistani-Muslim identity, claim friends, and chose to present himself as an exclusively westernised young man going by the nickname "Sid".
"He seemed to have more white friends than Asian friends," said one of his closest friends from school days, Rob Cardiss.
"He used to hang around with white lads playing football. And he was very English. Some of the other Pakistani guys used to talk about Muslim suffering around the world but with Sidique you'd never really know what religion he was from."
Biography Of A Bomber, presented by Nasreen Suleaman, is broadcast on BBC Radio Four at 2000GMT on Thursday.