Taimur Abdulwahab al-Abdaly showed little interest in religion as he was growing up in Sweden, channelling his energies into sport and partying.
But after he began attending Bedfordshire University in Luton “everything changed” as he became a strict Muslim with increasingly extremist views, even naming his baby son Osama in honour of the al-Qaeda mastermind Osama bin Laden.
On Saturday he blew himself up in a street full of Christmas shoppers in Sweden’s first suicide attack, after recording a message which promised to kill “your children, daughters, brothers and sisters” partly in revenge for the country’s support role in Afghanistan.
Abdulwahab’s radicalisation during his time in Luton once again raised questions over whether British universities are doing enough to stamp out the recruiting of extremists on campus.
In other developments:
* There were fears that Abdulwahab, 28, could have radicalised dozens of students after it was claimed that he preached at his old university in 2007, having been banned from his local mosque because of his extremist views.
* MI5 was investigating whether the bomber had links to other Luton-based terrorists, including one of the ringleaders of the 2004 fertiliser bomb plot.
* Counter-terrorism officers spent all day searching Abdulwahab’s semi-detached home in Luton, where he lived with his Romanian-born wife Mona and their three young children.
* The bomber’s wife denied having any prior knowledge of the plot, saying she was “devastated” by her husband’s death.
Iraqi-born Abdulwahab, who killed himself the day before his 29th birthday, grew up in the small town of Tranas, south of Stockholm, where his 61-year-old father worked in a factory.
A close friend said the family had been shocked by his transformation from an ordinary teenager to a religious fanatic after he left for Britain.
“There is no doubt that Taimur changed when he went to Britain,” said the friend, who spoke on condition of anonymity. “He would drink beer with his friends and go nightclubs. He didn’t care about politics or religion. He even had an Israeli girlfriend. He had many girlfriends, he enjoyed life.
“His parents were even a little worried that he was having too much fun. But then he went to England to study in 2001 and everything changed.
“When he came back he had grown a beard and he was very serious. He talked about Afghanistan and religion and did not want to hang out with his friends.
“His parents were worried about him but they thought he was just going through a phase. No-one ever imagined anything like this. Everyone who knew him is devastated. His parents are heartbroken.”
Teachers at Holavedskolan College in Thanas remembered him as “a quiet student” who liked basketball, and a former classmate who would only give his name as Khaled, said: “We used to hang out together, drink together and play practical jokes together. They were good times. I remember him as a college student chasing girls and drinking beer.
“But when he came back he was a changed man. He told me that something had happened when he was in (Luton). I am sure of this. Someone had taken advantage of him and had brainwashed him.”
Abdulwahab graduated from Bedfordshire University with a physical therapy degree in 2004, the same year that he got married.
He worked in a shop in Luton and began preaching his extremist views at the Luton Islamic Centre, also known as the Al Ghurabaa mosque.
Qadeer Baksh, the chairman of the mosque, said: “Some of the members brought it to my attention that his views were extreme so I challenged him. It was all about Iraq and Afghanistan. He was saying that Western governments had no right to be there and how too many Muslims remained silent.
“It was quite serious because some of the worshippers were starting to really listen to him.”
Mr Baksh said that in 2007 he challenged Abdulwahab, who “stormed out” and never came back. The mosque did not pass on concerns about Abdulwahab to the police.
He added: “I heard he’d gone to the Islamic Society at the university and continued to preach his extremist views.”
A spokesman for Bedfordshire University said they could “neither confirm nor deny” that the bomber had preached there.
Two years ago the Centre for Social Cohesion think tank warned in a report called Islam on Campus that radical Islam was increasingly taking hold in British universities, with a third of Muslim students who were questioned saying killing in the name of religion was justified.
Police and the security services have been concerned for years that British universities have become a breeding ground for terrorists.
MI5 is also investigating possible links between Abdulwahab and other high-profile extremists who have plotted terrorist attacks, including the July 7 bombers.
As investigators try to discover when and where he was radicalised, suspicion is centring on a small group of extremists who were former members of the banned group al-Muhajiroun.
The group, led by the preacher Omar Bakri Mohammed, became the focus of extremist activity in Luton and included among its members Luton resident Salahuddin Amin, one of the members of the fertiliser bomb plot who was arrested in March 2004.
Another key figure in Luton was Mohammed Quayam Khan, who knew the leaders of both the fertiliser gang and Mohammed Sidique Khan, the leader of the July 7 bombers who killed 52 people in 2005.
Anjem Choudary, the former head of al-Muhajiroun in Britain, told the Daily Telegraph he visits Luton “at least once a week” for meetings but added: “I can’t remember all the people I come across. His face and name are not familiar but Luton is a small place.”
He said the suicide bombing should be seen as a “severe warning” and “should not come as a surprise.”
Asked if her husband had told her what he was planning, Mona Abdulwahab, who runs her own beauty business, said: “No, of course not. I really don’t want to talk right now. I am very devastated and upset.”
Abdulwahab travelled to Syria two years ago, where it is believed he was trained in explosive techniques. He told his family he had travelled to the Middle East to find work.
Prosecutors in Sweden believe his bombs – which injured two bystanders – detonated prematurely, saving Stockholm shoppers from the carnage he intended.the full range of educational opportunities and resources designed to help them.”