June 1940: Britain is Hitler’s next target. But not everyone fears a Nazi invasion; some British citizens determine to do all they can to hasten it. Throughout WWII, Britain’s defence against the enemy within was Eric Roberts, a former bank clerk. Extraordinarily charismatic, he played his greatest role for MI5 – as Hitler’s man in London.

Codenamed Jack King, he single-handedly built a network of hundreds of British Nazi sympathisers, with many passing secrets to him in the mistaken belief that he was a Gestapo officer. Operation Fifth Column was so covert it was omitted from the reports MI5 sent to Churchill.

Robert Hutton reveals this astonishing story, told for the first time, in conversation with Helen Fry.

Robert Hutton is an author and UK political correspondent for Bloomberg News. He studied A.I. at Edinburgh University before going on to work at The Daily Mirror and The Financial Times.

Helen Fry is an historian and biographer and the author of more than 20 books focusing on intelligence, prisoners of war and the social history of WWII.