[1] In 1966 as a leading member of the National Union of Railwaymen (NUR),[2] Prendergast led a successful campaign to end racial segregation (the colour bar) in employment of London Underground rail stations, allowing black people to become station employees.

[5] In 1932 Prendergast joined the Irish Workers' Group,[3] a precursor organisation to the Communist Party of Ireland,[3] and in 1934 began studying at the Lenin International School in Moscow, before moving to London and joining the Communist Party of Great Britain (CPGB).

Jim Prendergast was an early volunteer for the International Brigades during the Spanish Civil War (1936-1939),[3] arriving in Spain on 12 December 1936 and almost immediately seeing combat in Cordoba near Lopera.

[3][4] Prendergast was attached to the XIV International Brigade which had no training, telecommunications, or air and artillery support, and as a consequence suffered high casualties at the hands of fascist forces.

[3][4] The military disaster for the International Brigades was later described by Jim Prendergast"My rifle is soon burning hot.

[4] Jim Prendergast wrote extensively in the Daily Worker on the capture Major Frank Ryan,[3] the leader of the Irish anti-fascists in Spain, who was detained for far longer than other international volunteers as a part of Nazi attempts to make contacts with the Irish Republican Army.

[3][4][7] In 1938 Jim Prendergast became one of the founding members of the Connolly Association (originally founded as the Connolly Club),[3] a charity and republican activist organisation that sought to support the Irish immigrant communities living in Britain and to forward Irish republican and socialist ideas.

[8] While selling copies of Irish Freedom near Marble Arch, Prendergast was arrested by the British police who falsely accused him of obstructing the highway.

[8] While he was detained, agents of the British government had broken into Prendergast's house and searched his belongings.

[3][8] During WWII, Jim Prendergast joined a group of volunteers consisting entirely of former International Brigade members,[3] engaged in research to develop diving equipment for the British military.

[3][8] After WWII, Jim Prendergast became a leading member of London's Irish communities, and began working as a guard for Marylebone railway station.

[3][8] One experienced guard known as Asquith Xavier, who was also a trade union member, received a letter telling him that his application for a job at Euston railway station had been rejected due to a ban on "coloured men" being employed as guards and porters.

[8] Helping both Prendergast and Xavier in their attempt to end the colour bar was the Morning Star, a British communist party newspaper that helped to publicise the plight of black workers and fought to end segregation in Britain.

[3][10] Jim Prendergast died on 31 May 1974, from injuries he sustained from falling down the stairs in front of his home in St Johns Wood Terrace.

[8] His remains were cremated in Golders Green Crematorium and were taken to Mount Jerome where they were placed in the grave of Jim's comrade Bill Gannon, who had also been an influential Irish communist.