after telling a local Conservative leader that the workers of Leeds would dispose of the "imitation Kaisers" of the city once they had done the same to the German Kaiser: however the case was eventually dismissed by the magistrate. He subsequently found employment as a storekeeper and in 1917 he joined the Socialist Labour Party, becoming a lecturer for the North East Labour College Committee in 1919, travelling the villages of the Great Northern Coalfield to teach classes on Marxism. In 1920, Jackson was a founding member of the Communist Party of Great Britain, although he was not present at the foundation congress. In the early 1920s, he paid visits to Dublin, where he met Constance Markievicz, Charlotte Despard and Maud Gonne, and Moscow, where he was introduced to Joseph Stalin, Sen Katayama and Clara Zetkin, although a planned meeting with Vladimir Lenin was cancelled due to the latter's illness. During the 1920s, he was a major figure in the CPGB, being on the Central Committee from 1924 to 1929 and editor of The Communist and The Sunday Worker. He was one of those arrested before the General Strike of 1926. He was removed from the leadership in 1929, essentially for opposing the ‘Left turn’ of the Third Period (which characterised the Labour Party as ‘social-fascist’), but remained a paid journalist for the CPGB, being a frequent contributor to the Daily Worker and writing several CPGB pamphlets. In the 1940s, he returned to his roots, working as a lecturer on Communist theory for the Party's Education Department, travelling across the country for eight or nine months of the year. Jackson was married to another SPGB founder member, Kate Hawkins, a socialist and suffragette descended from naval commander (and early slave trader) Sir John Hawkins and a cousin of Anthony Hope, the author of The Prisoner of Zenda. The couple had three daughters: Eleanor (who died in infancy), Stella and Vivien, who was a teacher at Summerhill School and married A.L. Morton. Kate died in January 1927, having been committed to Claybury Hospital due to declining mental health. Jackson married a second time later that year, to Lydia Packman: she died unexpectedly in 1943 following a minor operation. Before 1914 he was notable in the North and Wales, and for his flowing locks according to his obituary. His Manchester Guardian obituary said he was a "Marxist scholar of weight", and that