Born in Edinburgh, Todd was educated at Fettes College and Edinburgh School of Art. After a time in the office of his father, an architect, he worked for two years as an agricultural labourer on Mull. He then started a career in copy-writing and journalism, while writing poetry and novels, living in Edinburgh, London, and later Tilty Mill near Dunmow in Essex (later rented to poet and novelist Elizabeth Smart).

He was involved with the surrealists at the time of the 1936 International Surrealist Exhibition. During the 1930s, he friendly with Wyndham Lewis, contributing to the Lewis issue of Julian Symons's Twentieth Century Verse, and recruited him to keep the dozing Ezra Pound, whose portrait Lewis was painting. A character based on Todd was included in Symons' first detective story, The Immaterial Murder Case.) During World War II he was a conscientious objector. He moved to America in 1947, where he held a position at a university in New York, and ran the Weekend Press during the 1950s. He contributed to children's literature, with the fifties Space Cat series.

He was married to sculptor Joellen Hall Rapée (1921-2006). In 1958, he settled in Majorca, Spain. He spent the remainder of his life there until his death in 1978.