Brennan moved to St Ives, Cornwall in the early 1950s as a self-taught painter and supported himself by waiting tables in a local cafe. There he met David LEWIS, also waiting tables prior to deciding what routes in art to follow. Later Lewis would write the introduction to the exhibition catalogue for a solo show by Brennan, and he is mentioned in Lewis's memoir to introduce the Tate publication about 25 years of art in St Ives [ref]. He was elected a member of the Penwith Society in 1957, and developed an interest in monotypes. In 1970 he spent three months working in Holland.