Keynes's support for the arts was extensive and took various forms. During the 1930s The New Statesman was his main vehicle for the promotion of plays, of the Camargo Ballet, and of productions at the Arts Theatre, Cambridge. In addition, he wrote anonymous ‘puffs’ and short comments for the columns of The Nation and Athenaeum, prefaces to exhibition catalogues, longer articles, and letters to the press.

These years also saw the growth of Keynes's private collection of paintings, started in 1918 when he went to the sale in Paris of Degas' private collection. On that occasion he also had a Treasury Grant of £20,000 for purchases for the National Gallery.

Over and above all this, of course, came his contributions of time, effort and money to the arts in Great Britain. He was a buyer for the Contemporary Arts Society; treasurer of the Camargo Ballet Society (1931–5); and a Trustee of the National Gallery from October 1941. From February 1942 he was Chairman of the Council for the Encouragement of Music and the Arts (C.E.M.A.), which in 1945 became the Arts Council; and, at the end of the war, Chairman of the Trustees of the Royal Opera House, Covent Garden. Finally, there was the founding, building and nourishing of the Arts Theatre, Cambridge, and its presentation in 1938 to the University and the people of Cambridge.

The London Group of artists had emerged as an amalgamation of several small groups of artists who had been unhappy with the state of painting in Britain at the end of the first decade of this century.