Rubens was born in Cardiff in 1923. She was educated at Cardiff High School for Girls and later studied English at the University of Wales, Cardiff, where she was awarded her BA in 1947. Later, Rubens taught at a grammar school in Birmingham and then in London, before moving onto the film industry where she made documentaries. Many of her novels drew on her own Jewish family childhood in Cardiff. Her fourth novel, The Elected Member, won the Booker Prize for Fiction in 1970.