During the First World War, Frampton served in the British Army on the Western Front with a field survey unit, sketching enemy trenches, and also worked on the interpretation of aerial photographs. After the war Frampton resumed his artistic career and established himself as among the most highly regarded of British painters during the period. Between 1920 and 1945 he exhibited at the Royal Academy nearly every year, showing a total of thirty-two paintings there. Frampton was an early member of the Society of Graphic Art and exhibited there in 1921. In 1925 he was elected a member of the Art Workers Guild. In 1934 he was elected an Associate of the Royal Academy and in 1942 became a full member of the Academy. Frampton painted portraits of the Duke of York, who was to become King George VI, academics and scientists, and a series of full length portraits of women from fashionable society. He would often spend an entire year working on a single painting. Frampton painted in smooth colours without visible brushstrokes, achieving a look of almost photographic realism. Most of his paintings were commissions, but a notable exception was Portrait of A Young Woman, which Frampton showed at the Royal Academy in 1935 and which was purchased for the Tate. Frampton had several of the objects in the painting made specially for the painting and his mother made the dress worn by the model, Margaret Austin-Jones. She modelled for him again in one of his most famous works, A Game of Patience, now hanging in the Ferens Art Gallery in Hull.
During World War Two, Frampton received two commissions from the War Artists' Advisory Committee. One was intended for the Admiralty, but a suitable subject was not found and the painting was never made. Frampton's other WAAC commission was for a portrait of Sir Ernest Gowers, which became a triple portrait of Gowers and his colleagues in their underground control room in Kensington. In 1953 Frampton requested that the Royal Academy place him on its list of retired members. His eyesight had begun to worsen, convincing him that he could no longer paint to his previous high standard and with such meticulous detail. With his wife he moved to a hilltop house overlooking Monkton Deverill in Wiltshire. Frampton had designed the property in the 1930s and for the rest of his life he worked on improving and maintaining this house, which included his own furniture and clock designs. For many years Frampton's art was rarely shown in public and he was largely forgotten. However, he lived to see his retrospective at the Tate in 1982. It was his first one-man show and greatly restored his standing.
