Gillett submitted cartoons to the periodical Fun before starting work full time as an illustrator at The Daily Graphic from 1898.
[3][4] Gillett worked in pen and ink, pastel, watercolour, and oil and was noted as a skillful caricaturist.
[6] Gillett also illustrated 25 reissues of works by G. A. Henty as well as several books by Robert Louis Stevenson and Percy F.
[3] Two of Gillett's works, La Finale and Contre l'horizon, were submitted into the Mixed Painting, Drawings And Water Colours category at the 1928 Summer Olympics.
He did not win a medal but his entry makes him one of only a small number of posthumous Olympians and the only one to represent Great Britain.