Rob Sewell was born and brought up in the working-class neighbourhood of Penlan, in Swansea, South Wales. His grandfather was an early member of the British Communist Party and his mother was also a life-long party member.
Rob was active in the Labour Party Young Socialists and he was elected to represent Wales on its National Committee in the mid-1970s. He became a full-time worker for the Militant and went to work at its headquarters in 1982. He served on its leading body from 1974 to 1991. In 1992, together with Ted Grant and Alan Woods, he helped launch the Socialist Appeal journal, and then the website In Defence of Marxism.
He is currently the editor of the Socialist Appeal newspaper and plays a leading role within the International Marxist Tendency.