As a World War rages, humanity stands on the precipice of a new era in warfare. The atomic age is dawning - and Earth's great powers are determined to secure their place in it.

In these episodes of True Spies, Sophia Di Martino meets the spies who shared nuclear secrets that still influence global geopolitics today. In Part 1, Professor Emeritus of Theoretical Physics at Oxford University, Frank Close, tells the story of the scientist who helped Soviet Russia build the bomb - Klaus Fuchs.

From SPYSCAPE, the home of secrets. A Cup And Nuzzle production. Series producers: Gemma Newby, Joe Foley. Produced by Hannah Dean. Music by Nick Ryan.

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