Maajid Nawaz is a British-born Muslim who became a radical Islamist.
He was arrested and imprisoned in Hosni Mubarak's Egypt but when he emerged from prison he renounced his former views and launched a campaign to counter Islamist ideology.
He tells Stephen Sackur what it was that brought him to those radical beliefs in the first place.
You can watch the full interview on BBC World News on Tuesday 14 at 03:30, 08:30, 15:30 and 20:30 GMT and on the BBC News Channel at 04:30 BST on Tuesday 14 August 2012 and 00:30 BST on Wednesday 15 August 2012
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