Dr Antony McRoy said that Khalid Masood - as a 52 year old Muslim convert - was not a typical terrorist, meaning surveilance staff may need to expand their survelience criteria in future.
The radicalisation expert and Islamic studies lecturer said: "It's unusual to have a middle-aged man involved.
"It's not completely unprecedented but it's unusual ...that means that the security services will have to alter their surveilance on a much wider demographic."
A keen schoolboy footballer, Masood was born Adrian Russell Elms to a single mother in the Kent town of Dartford on Christmas Day in 1964.
He grew into a troubled adult, spending various spells in prison - including a two-year stint over a fight near Rye in East Sussex which left a man needing 20 facial stitches.
Explaining the challenges presented by Muslim converts who resort to terrorism, Dr McRoy went on to say: "If they're [terrorists] either from an Afro-Caribbean background or indigenous white background or whatever, it's much easier for them to revert to their original names, shave off their beards or remove their hijabs if they're women, and just disappear among the wider population."
Dr McRoy said the apparent radicalisation of Mr Masood raises questions for the Christians living around him.
He continued: I think we've got to ask a question; the question here in regard to this man, he was a convert to Islam, why did he not become a convert to evangelical Christianity?
"What it that there were no evangelical Christians around to talk to him, did they not have answers to his questions?"
Listen to Premier's Alex Williams speaking with Dr Anthony McRoy: