Now we know the identity of ‘Jihadi John'. Mohammed Emwazi is a British-reared university graduate who turned his back on a Western way of life to become the poster boy for Islamic State.

His unmasking followed the shocking story of three East London teenage girls fleeing their loving families and promising educational futures to make a perilous trip to Syria to join the jihadists. What could entice these and 500-plus other British citizens to abandon their relatively prosperous lives in a free society to join a vicious band of nihilists?