In 1923, Gross entered the Slade School under Professor Henry Tonks, and studied there from January to June. During the summer term he also attended evening classes in etching with W P robins at the Central School of Art. In the Autumn, Gross moved to Paris where he studied painting under Piere laurens at the Académie Julian and engraving under C.A. Waltner at the École des Beaux-Arts.
In 1925, Gross held his first one-man show at the Abbey Gallery, Victoria Street, London (W R Deighton & Sons). He showed oil paintings, watercolours, and 34 etchings of France, Morocco and England.
Gross was appointed Official War Artist with the rank of Army Captain. Gross embarked on troopship Highland Monarch at Avonmouth, bound for the Middle East via the Cape. In 1942 he painted the ' Convoy' series aboard the ship from the North Atlantic to Suez, Sierra Leone, the Cape, the Indian Ocean and Aden. The year after, in 1943 Gross had a one-man show at the National Gallery, 'India in Action', which then toured Australia and North America. In all, as a War Artist, Gross estimated having painted some 500 pictures. His work is well-represented in public and private collections across the world.
Gross was appointed a CBE in 1982 and died 8 September 1984 .