Every time there's a terrorist attack that makes national headlines, the same talking heads seem to pop up like an obscene game of "whack-a-mole". Often they appear one after the other across the media circuit, bobbing from celebrity television pundit to erudite newspaper outlet.
A few years ago, BBC Newsnight proudly hosted a "debate" between Maajid Nawaz, director of counter-extremism think-tank, the Quilliam Foundation, and Anjem Choudary, head of the banned Islamist group formerly known as al-Muhajiroun, which has, since its proscription, repeatedly reincarnated itself. One of its more well-known recent incarnations was "Islam4UK".
Both Nawaz and Choudary have received huge mainstream media attention, generating press headlines, and contributing to major TV news and current affairs shows. But unbeknown to most, they have one thing in common: Britain's security services. And believe it or not, that bizarre fact explains why the Islamic State's (IS) celebrity beheader, former west Londoner Mohammed Emwazi – aka "Jihadi John" - got to where he is now.