During World War I Macaulay worked in the British Propaganda Department, after some time as a nurse and later as a civil servant in the War Office. She pursued a romantic affair with Gerald O'Donovan, a writer and former Jesuit priest, whom she met in 1918; the relationship lasted until his death, in 1942. During the interwar period she was a sponsor of the pacifist Peace Pledge Union; however she resigned from the PPU and later recanted her pacifism in 1940. Her London flat was utterly destroyed in the Blitz, and she had to rebuild her life and library from scratch, as documented in the semi-autobiographical short story, "Miss Anstruther's Letters", which was published in 1942.