During early 1923 the Mars I was given extensively modified wings, had the fuel and water header tanks transferred within the fuselage to lose the view-limiting cabane structure, and had a more powerful Lion engine installed, being re-designated Gloster I. After winning the Aerial Derby of 1923 it was acquired by the RAF and, with float landing gear, was used by the RAF's High Speed Flight at Felixstowe for training purposes.