Born in Stockport, England, Green was schooled at A. S. Neill's Summerhill, while his parents fought in the International Brigades during the Spanish Civil War. Green co-founded the literary periodical Nimbus with Tristram Hull and later worked as an editor at MacGibbon & Kee, where he published alongside Tim O'Keeffe. They formed their own publishing house, Martin Brian & O'Keeffe, with the editor Brian Rooney. Here, Green collected and published Patrick Kavanagh following the suggestion of the painter Patrick Swift and the poet Anthony Cronin. . Green also published books by Flann O'Brien, Hugh MacDiarmid, Francis Stuart, Colin MacInnes, Robert Graves, Frank Sargeson, Paul Potts and many other writers.
Green published eight books of his own, as well as four plays, and contributions to numerous other publications including The Other Jerome K Jerome (1984) and Myles Away from Dublin (1985). He has six children and lives in Newlyn, Cornwall, with his cat Nefertiti.