Cliff Slaughter's life (1928-2021) was dedicated to working-class internationalism and socialist revolution. A scholarship boy in post-World-War-II Cambridge he became a university lecturer in his native Yorkshire doing important work in social anthropology. But it was the theory and practice of Marxism that guided him. After leaving the Communist Party at the time of the 1956 Stalinist crisis, he joined the Trotskyist group led by Gerry Healy and worked tirelessly for the Socialist Labour League, the Workers Revolutionary Party (WRP) and the International Committee of the Fourth International. Increasingly at odds with Healy's political prognoses, pragmatic practice and subjective philosophising, Slaughter finally broke with him in 1985, when his morally corrupt, abusive exploitation of idealistic young comrades was exposed.