Question:  Leonard "Len" Benker Johnson organized a concert and a rally featuring an American bass singer who became involved with what?
Sentence (from "Len Johnson (boxer)"): Following the Second World War, he was a co-founder of the New International Society in Manchester, which provided a vehicle for black political and social self-organisation in the city and campaigning against racism at home and abroad, including organising a concert and a rally featuring Paul Robeson in support of the Trenton Six, which were both attended by 10,000 people.
Relevant evidence: Yes