Al-Qaeda leader Anwar al-Awlaki 'radicalised in London'
A new report has said prominent al-Qaeda leader Anwar al-Awlaki was radicalised during his time in London.
Since going on the run in Yemen in December 2007, Mr Awlaki's overt endorsement of violence as a religious duty in his sermons and on the internet is thought to have inspired new recruits to Islamist militancy.
US officials say he is also a leader of al-Qaeda in the Arabian Peninsula, an offshoot of the militant network in Saudi Arabia and Yemen, and helped recruit Umar Farouk Abdulmutallab, the Nigerian accused of attempting to blow up an airliner as it flew into Detroit on 25 December 2009.
His internet sermons have also said to have inspired Roshonara Choudhry to stab east London Labour MP Stephen Timms, her trial heard last year, and he also plotted with British Airways employee Rajib Karim to attack planes flying from Heathrow.
When and how Awlaki went from being a mainstream and moderate preacher to openly justifying attacks on civilians is a matter of contention.
For many it started with his incarceration in Yemen in 2006.
But a new report by the International Centre for the study of Radicalisation, due out on Monday but seen by BBC London, claims it was much earlier, and in London, that he began his journey to extremism.
The report's author Alexander Hitchens says that when Awlaki arrived in the capital - after 9/11 but before the 7/7 London attacks - he found figures such as Abu Hamza "openly preaching support for Al Qaeda with the authorities taking little action against them.
He said: "So Awlaki felt safe exploring and expressing extreme views.
"He was promoted by a number of institutions in London at the time and that enabled him to gain a large following of British Muslims - some of whom are still with him to this day."
But Muddassar Ahmed, who runs a PR firm in London, said he remembers the cleric in a very different way.
He attended a series of lectures on early Islamic history given by Awlaki back in 1999 while visiting from the US, and says he showed no signs of extremism.
He said: "At the time he was a very charismatic, knowledgeable, charming preacher.
"Years later when I realised Anwar al-Awlaki was now public enemy number one and the Bin Laden of the internet I was shocked at his transformation."
While in the capital, he spoke at a number of mainstream Muslim institutions and according to some, Awlaki's message was often far from moderate.
Rashad Ali is a former member of Islamist group Hizb-ul-Tahir and attended some of Awlaki's lectures, and is now director of think-tank Centri.
"He was very clear about having this revolutionary jihadist approach," Mr Ali said.
"He started delivering lectures on jihad that came out in 2003.
"He gave very explicit verdicts on suicide bombing being religiously acceptable, about the enforcement of religious law and about how jihad in its medieval military form is still necessary today as an imperialist objective."
Usama Hasan, an Imam from east London, was also worried by a sermon of Awlaki's that he attended, which discussed the arrest of British Muslim terror suspects.
In it, Awlaki called on his audience not to co-operate with the authorities in terrorism cases.
Mr Hasan said: "His approach was all about us versus them which concerned me.
"I thought his talk was likely to inflame people's tensions but not tell them what to do. That troubled me."
Security services are said to be so concerned by Awlaki and his influence that according to reports, a US drone attack in May in Yemen targeted but failed to kill him.
So 10 years on from 9/11, but with the threat of international terrorism ever present, they will be hoping any missed opportunities in not confronting him while in London, will not come back to haunt them.