He served as the only secretary for the Trustees for the Establishment of the Colony of Georgia in America from 1732 to 1752.
[1] Before he was retained by the Georgia trustees, Martyn authored a well-received tragedy, Timoleon, in 1730, an effort supported by Alexander Pope.
[2] Martyn was retained by Anthony Ashley Cooper, 4th Earl of Shaftesbury, a Georgia trustee, to write a biography of his great-grandfather, Anthony Ashley Cooper, 1st Earl of Shaftesbury.
The 1st earl was a notable figure in seventeenth century English politics and with philosopher John Locke designed the settlement plan for the Carolina Colony.
[3] Martyn authored several publications for the trustees on the colony, including "Some Account of the Trustees Design for the Establishment of the Colony of Georgia in America," based on a tract written by James Oglethorpe.