Neumann had previously been very active in the Social Democratic Federation, being a public speaker for that party and secretary of its Chelsea & Fulham branch in 1897.

Neumann was a well-known early Impossibilist, being a victim of the expulsions of April 1904 which led to the foundation of the Socialist Party of Great Britain in June.

A notable indoor and outdoor speaker for the SPGB (billed as Newman), he was also an enthusiastic writer for the Socialist Standard, translated foreign-language articles (including the pamphlets based on Kautsky’s The Class Struggle (Erfurt Program)) and was the author of the Party song (“The World for the Workers”).

Along with Henry Martin, he had been a member of the Provisional Committee of 1911 which opposed notional Socialist MPs ever voting for reforms (the ‘WB of Upton Park affair’) and probably resigned on that issue.

He was interned because of his German origin during the First World War where he met Rudolf Frank, co-founder of the Bund Demokratischer Sozialisten, the Austrian counterpart to the SPGB.