During the 1920s he worked in various textile design jobs in Manchester — for Tootal, Broadhurst, Lee & Co, the carpet manufacturers, H&M Southwell, and John Lewis Partnership. He took up painting seriously in 1928, and taught design at the Central School of Arts and Crafts, London, from 1929.
In 1931 he exhibited at the Royal Academy and with the London Group, which he joined in 1934. In 1933 the Tunnards moved to Cadgwith, Cornwall, where they ran a business making printed silks. From the mid-1930s, he became friends with Julian Trevelyan, Henry Moore, John Betjeman and Humphrey Spender.
From 1945 to 1965 he taught at the Penzance School of Art. He exhibited again at the Royal Academy in 1960, and was elected as an Associate in 1967. He died in Penzance in 1971
Tunnard was given a show at the Guggenheim Jeune gallery in 1938. In her autobiography, Peggy Guggenheim says that "His color was exquisite and his construction magnificent" and that "I was happy to think that I had discovered a genius." She purchased a large work from the exhibition titled PSI which is in the Guggenheim Collection in Venice.
Interest in his work diminished after his death in 1971. In 2000, there was a centenary exhibition at Durham University.
A major retrospective at Pallant House Gallery in Chichester in Spring 2010 entitled 'John Tunnard: Inner Space to Outer Space', explored the themes of abstraction, music and surrealism, nature and landscape, and science and space travel in his work. The exhibition was curated by Simon Martin.Wikipedia