As a very young man he moved in London literary circles championing traditional verse and writing as opposed to modernism. He ran the Twyn Barlwm Press, a small press publishing some well-known poets, its title inspired by the mountain Twyn Barlwm in South Wales, beloved by one of his literary idols Arthur Machen. Machen was one of the surviving writers of the 1890s he admired and befriended. Gawsworth's longest piece of written work was a biography of Machen, but he could find no publisher for it in the thirties. It was finally published by Tartarus Press in 2005. Other writers Gawsworth admired were Edgar Jepson and M. P. Shiel, whose literary executor he would later become. In 1931 he had the poem In Winter by W. H. Davies privately printed in a limited edition of 290 numbered copies, illustrated by Edward Carrick and all individually signed by Davies. A further special limited edition of 15 were printed on handmade paper and also hand-coloured by Carrick. Three companion titles appeared in similar editions at the same time: In Spring by Edith Sitwell, In Summer by Edmund Blunden and In Autumn by Herbert Palmer. He gave Hugh MacDiarmid a roof over his head in London in 1934. At this time he was very much involved in compiling story collections, generally of the fiction of the supernatural. Poetry collections of this time were Lyrics to Kingcup, Mishka and Madeleine. A Poem Sequence for Marcia, Poems 1930–1932, New Poems 1939. Later he published through the Richards Press. He met and befriended the young Lawrence Durrell in 1932, when Gawsworth was living in Denmark Street. He made friends as well as enemies throughout literary London.
WW2
During World War II, he served in the Royal Air Force as an aircraftsman in North Africa. As one of the Cairo poets, he made a more serious name for himself, being part of the group. Later he returned to a picturesque eccentricity as a Fitzrovian. His Collected Poems appeared in 1949. A later volume is Toreros. The Known Signatures anthology was prompted by the Michael RobertsNew Country collection. The Edwardian Poetry Book One and Neo-Georgian Poetry 1936–1937 are extraordinary for their retrospective vision.
As literary executor to M. P. Shiel, Armstrong also inherited the throne of the Kingdom of Redonda styling himself H.M. Juan I. The independent publisherJon Wynne-Tyson became Gawsworth's literary executor in 1970, also becoming H.M. Juan II. But Wynne-Tyson "abdicated" in favour of the Spanish novelist and translator Javier Marías— H.M. Xavier I – who became both Shiel's and Gawsworth's literary executor. According to John Sutherland's Lives of the Novelists, "the excessively minor poet John Gawsworth" kept the ashes of M. P. Shiel "in a biscuit tin on his mantelpiece, dropping a pinch as condiment into the food of any particularly honoured guest".