One episode delves into the mystery of MI5 agent ‘Jack King’. During World War II, a network of British fascists gathered secret information that might help the Nazi cause and hasten their own country’s defeat. They thought they were passing these secrets to Jack King, a Gestapo officer who had been planted in England. In 2014, files revealed ‘Jack’ was a man called Eric Roberts – a top secret agent who really worked for MI5.
So who was the man behind ‘Jack King’? How did he infiltrate fascist groups? Was there really a ‘fifth column’ aiming to undermine Britain from within? And if it didn’t exist… would MI5 have to invent it?.