Around 2019, during my research on Leon Turrou, I contacted his descendants, including his grandson Bob. He had limited knowledge about his grandfather's biography and referred me to Richard Bareford and Rhodri Jeffreys-Jones.
Rhodri Jeffreys-Jones The Nazi spy ring in America
Rhodri Jeffreys-Jones is a historian and professor at the University of Edinburgh in Scotland. At the time, he was finishing his book on Leon Turrou, titled "The Nazi Spy Ring." His work portrays Leon Turrou, an FBI agent in the 1930s, in a very (perhaps too) favorable light. Bertrand Patenaude wrote a critique of the book published in the WSJ.
