Jefferys enrolled at the Royal Academy and his talent was marked with a gold medal for a drawing titled Seleucus and Stratonice in 1773.

[2] The Dilettante Society underwrote the expense of three years in Rome after a recommendation by Sir Joshua Reynolds.

Jefferys stretched this to four years and returned with a number of well regarded classical drawings of violent subjects, but no paintings are known.

[3] Jefferys died in Soho, London, unmarried, from a cold at the end of January 1784.

Many drawings by Jefferys were erroneously attributed to James Barry and John Hamilton Mortimer until they were reassigned in the 1970s.