 Fuchs was released on 23 June 1959, after serving nine years and four months of his sentence (as then required in England where long-term prisoners were entitled by law to one-third off for good behaviour in prison) at Wakefield Prison and promptly emigrated to the German Democratic Republic (East Germany). A tutorial he gave to Qian Sanqiang and other Chinese physicists helped them to develop the first Chinese atomic bomb, the 596, which was tested five years later — according to Thomas Reed and Daniel Stillman, the authors of The Nuclear Express: A Political History of the Bomb and Its Proliferation (2009). Three historians of nuclear weapons history, Robert S. Norris, Jeremy Bernstein, and Peter D. Zimmerman, challenged this particular assertion as "unsubstantiated conjecture" and asserted that The Nuclear Express is "an ambitious but deeply flawed book".
