[3] He also designed book jackets for his friends: Flann O'Brien's The Dalkey Archive and Dominic Behan's The Public World of Parable Jones.

[5] In the 1940s and early 1950s, he and his first wife ran what evolved into a literary salon on Dublin's Grafton Street, including John Ryan, Anthony Cronin, J. P. Donleavy, Brendan Behan, Carolyn Swift, Dan O'Herlihy, Patrick Kavanagh, Erwin Schrodinger and Gainor Crist who was the model for the protagonist in The Ginger Man.

[7][8][9][10] This post-war Dublin bohemian scene was immortalized in Donleavy's novel, The Ginger Man, where MacNamara appears as MacDoon, the Kangaroo-suited artist.

He taught art at the Marylebone Institute, contributed reviews to the New Statesman and other periodicals, and published books on picture framing, the artistic uses of papier-mache, and on puppetry.

Upon retirement from teaching, he added a biography of Éamon de Valera, aimed at young readers, and two seriocomic works of fiction.