[[FBI]] eavesdropping surveillance in 1945 on a conversation between [[Philip Jaffe]], [[Andrew Roth]], and [[Theodore Cohen]] of the Foreign Economic Administration revealed them discussing the charges brought against Greenberg of the FEA by the Civil Service Commission. Greenberg had been charged with Communist connections and affiliations. Jaffe, in referring to Greenberg's case, stated that Lauchlin Currie "was the guy who could help" but refused to furnish assistance.
Upon return to [[United Kingdom|England]], Greenberg went back to Cambridge and completed work on his Ph.D. thesis, which was eventually published as a book [httphttps://www.amazon.com/exec/obidos/tg/detail/-/0853454973 "British Trade and the Opening of China"] (1947, [[Cambridge University Press]], reissued in 1970, republished in the USA in 1979, and again in 2000 as part of an 8 volume set "China Trade : British Commerce and the Opening of China, 1635-1842"). This book, based on the then recently released archives of the [[Jardine Matheson]] Company, a major player in the development of Hong Kong, describes the forceful exploitation of China by British colonial power in establishing and maintaining the colony of Hong Kong (see also [[Opium War]]).
Blocked from academic promotion, most likely due to his left-leaning politics, he went on to work in a number of jobs in journalism, public relations, advertising and film criticism in England, Switzerland and France. He lost his U.S. citizenship due to absence from the USA and was denied a passport by the British Home Office, even as late as the 1970s. His British passport was never restored to him, and the accusations continued to hound him throughout the 1950s.