A former friend who studied with British-born Bilal Abdulla at Cambridge said last night that the Iraqi had watched a video of a man being beheaded before warning that was what happened to people who were not devout.

Shiraz Maher described how Dr Abdulla, who has been implicated in the Jeep attack on Glasgow airport, was an avid admirer of Abu Musab al-Zarqawi, the ruthless late al-Qaeda leader in Iraq. Mr Maher, a former member of a radical Islamic group, said Dr Abdulla had believed in an Islamic state and Sharia, and wanted to “expand it across the entire world”.

There were also separate claims that Dr Abdulla may have been recruited by al-Qaeda in Iraq and ordered to travel to Britain to hand-pick other Muslim doctors to form a sleeper cell.

Dr Abdulla was born in Aylesbury, Buckinghamshire, where his father, also a doctor, worked.

Mr Maher told BBC Newsnight that he became close friends with the Iraqi when the pair were in Cambridge together in 2004, even introducing him to his family. He said Dr Abdulla, who was training to be a doctor, was angry about the situation in Iraq and supported the insurgency there.

“He actively cheered the deaths of British and American troops in Iraq,” said Mr Maher, who was a member of the radical Islamic group Hizb utTahrir but has since renounced its extreme ideology. Dr Abdulla suffered a personal loss when a friend of his was killed in Iraq by a Shia militia gang.

“[He] also supported, which was quite unusual, the sectarian conflict, and so supported the Sunni attacks on the Shias,” Mr Maher said.

He told how his former friend shared a house with a non-practising Muslim who he castigated for not praying five times a day and for playing a guitar. He said he showed his housemate a video of al-Zarqawi beheading a man and warned him that he had better start praying. Police have been making inquiries in Cambridge, where Dr Abdulla reportedly has several relatives. He lived there briefly in 2001 and again in 2004.

His family are Wahabist Muslims, an ultra-conservative form of Islam that promotes Sharia law.

His father, Talal Abdulla, studied as a rheumatologist in Britain and had a private clinic in Baghdad until two years ago when he fled to Irbil in northern Iraq after being threatened by the Shia Mahdi Army.

Bilal Abdulla returned to Britain after graduating from medicine in Baghdad in 2004, securing a job as a junior doctor at the Royal Alexandra Hospital in Paisley. He also reportedly spent time in the Houston area of Glasgow where the second man in the Jeep, Dr Khalid Ahmed, lived.

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