An expert in religious extremism told of his shock after learning two former friends had carried out the 2007 attack on Glasgow Airport.

Shiraz Maher, an ex-member of Hizb-ut-Tahrir turned peacemaker, told Tory delegates how he was stunned to see his former acquaintances in televised coverage of the atrocity.

Mr Maher, now a researcher into extremist thinking said he knew both men while a student at Cambridge University during 2004 while mixing in Islamist circles.

He told a fringe meeting in Manchester: "One of the guys was just a normal guy from India. He wasn't interested in jihad and didn't see the point. But fast forward three years later and I am seeing his suicide notes on the BBC websites.

"What you find is suicide bombers aren't acting in a vacuum, they feed off an ideological base that supports their thinking and encourages them to think what they are doing is right."

The researcher, who left the extremist group after reflecting on the nature of Islam during his studies, said many young British Muslims had been attracted by its ideology in the wake of 9/11.

He added: "The support was flowing from youngsters who were fundamentally confused at the time. There was the question of whether they were British or Pakistani, Westerners or immigrants. Being told that you are actually part of a club with 1.2 billion members around the world is quite an attractive message."

He accused previous government ministers of trying to 'appease' various extremist groups, which had unintentionally legitimised them.

The fringe meeting on political extremism was organised by the International Centre for the Study of Radicalisation at King's College and Jewish charity The Community Safety Trust.

The meeting also heard from Matthew Collins, a former BNP and Combat 18 member who now works for anti-fascist group Searchlight.