Born in 1921 in Llanfihangel Crucorney, near Abergavenny, Wales, Williams was the son of a railway worker. He was 14 when the Spanish Civil War broke out and joined a local Left Book Club
In 1937, he saw the Soviet pavilion at the International Exhibition in Paris, and bought a copy of The Communist Manifesto.
Williams attended Trinity College, Cambridge, where he joined the Communist Party and its Writers’ Group in 1939. He also took part in the Socialist Club and became a delegate to the National Congress of Student Unions. Along with Eric Hobsbawm, he wrote a pamphlet about the Soviet-Finnish War, and Williams was editor of a university journal.
In late 1940, he enlisted in the British Army, but stayed at Cambridge to take his exams in June 1941, the same month Germany invaded the Soviet Union.
His membership in the Communist Party lapsed without him ever formally resigning as he began serious involvement in the war. He was part of the invasion of Normandy and later served as a tutor in adult education at the University of Oxford for several years.
Williams' own political position was a humanist Marxism. In 1951 he was recalled to the army as a reservist to fight in the Korean War but refused to go.
His `Culture and Society' was published in 1958 and others followed. Williams was invited to return to Cambridge in 1961, eventually becoming Professor of Drama.
He was a key figure in 1967 in the publication of the New Left May Day Manifesto even tually published by Penguin for May Day 1968. He and many other former members of the Communist Party showed a readiness to work with the Communist Party.
By the 1970s, he was a Plaid Cymru member.
He retired from Cambridge in 1983, Amongst his later works is `Loyalties', a novel about 1930s Communism. He was also working on People of the Black Mountains, an experimental historical novel about people from the part of Wales he came from.
Williams died in 1988.