Eddie Chapman: rogue, criminal, confidence trickster, hero to both sides and betrayer of all. At the start of the Second World War, Chapman was recruited by the German Secret Service.

He was a highly prized Nazi agent. He was also a secret spy for Britain, alias Agent Zigzag. "Agent Zigzag" is the untold story of Britain's most extraordinary wartime double agent. Genuinely courageous, able to withstand withering interrogations from both sides, Chapman was a dashing, charming and fiercely intelligent man whose talents led to a single end: breaking the rules.

He wore loud suits, drove fast cars, and had a woman in every port. Yet, at the same time he was, in his own way, loyal to his lover and their child. This was a man who courted contradictions as much as he courted adventure. Inside the traitor was a man of loyalty; inside the villain was a hero; the problem for Chapman, his spymasters, and his lovers, was to know where one ended, and the other began.

In 1943, Colonel Tim Stephens of MI5 said of the story of Chapman: 'In fiction it would be rejected as improbable.' MI5 have only just released the material on Chapman, and Macintyre has full access to all of Chapman's manuscripts, letters and photographs. What emerges from this trove is an exhilarating true story of loyalty and betrayal, courage and cowardice, a crook who was also a hero.

It is one of the most gripping untold stories of the Second World War.