Jihadi John

It was a defining moment, the first time ‘Jihadi John’ appeared. Suddenly Islamic State had a face and the whole world knew the extent of their savagery. Weeks later, when his identity was revealed, Robert Verkaik was shocked to realise that this was a man he’d interviewed years earlier.

Back in 2010, Mohammed Emwazi was a twenty-one-year-old IT graduate who claimed the security services were ruin...