Afzal Ashraf, a consultant fellow at the Royal United Services Institute said turning to extremism allowed those with criminal pasts to continue breaking the law with an “air of spirituality”.
He is thought to have previous convictions including assault and GBH and reportedly converted to Islam whilst in prison.
Host Julia Hartley-Brewer said: “It’s interesting how many of them will have criminal pasts, they will have been known to the authorities, this man for GBH, for a knife attack, other assaults as well, and how much criminality seems to be involved now with Islamic extremism.
Afzal Ashraf said criminality was a "major part" in driving people to extremism
It's criminality but they give it an air of spirituality or morality
“Is it that these people are easy-pickings in jail and that’s where they’re radicalised or is it that they’re already on the fringes of society and therefore they’re targeted that way, what’s going on there?”
Mr Ashraf, who worked as a counterterrorism strategist in Iraq, said extremism was very much to do with “criminal tendencies”.
He said: “I think it’s that their criminal tendencies make them very much more vulnerable to the idea that you can carry on doing what you’re doing.
“[It’s] criminality but [they] give it an air of spirituality or morality because deep down everybody knows the difference between right and wrong, it doesn’t matter what our backgrounds are.
London terror attack: Latest pictures Fri, March 24, 2017
4 dead and 40 injured in London terror attack
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Armoured police personnel carriers are seen on a street leading to the Houses of Parliament in central London on March 24, 2017 two days after the March 22 terror attack on the British parliament and Westminster Bridge
London attacker Khalid Masood reportedly had previous convictions
“What it does do is, this sort of thing allows them to feel that what they’re doing is less wrong, [that] it is actually good and so yes, criminality is a major part.”
Mr Ashraf suggested how terrorists could be deterred in future and called for countries to "counter the impression of success of these organisations and make them fail politically”.
A police investigation is now ongoing after Masood mowed down members of the public before attempting to storm Parliament, killing a policeman in the process.
Three members of public died as a result of the attack.