Jeffreys seems to be a pretty eclectic writer, publishing plays (of varying success), verse (some of which published in GM), an oratorio, extempore epigrams, and translations from Latin and French. He was a close friend of Duncombe's, contributed versions of several of Horace's odes to Duncombe's translation of Horace, and was the dedicatee of at least one of Duncombe's translated versions. According to his obituarist, Jeffreys passed most of his life at leisure in the houses of his relations, the dukes of Chandos.