Returning from the war of 1914-18, where he lost a leg, James went into partnership with Charles Murray Hennell in 1919, full of enthusiasm for the ideals of a new social order. He lectured on “Housing and Site Planning,” at the Architectural Association in 1921-22, and published a book Small Houses for the Community with photographs by F. R. Yerbury, in 1924. Both Hennell and James had worked at Letchworth, and much of their early work together was at Welwyn Garden City. They were also responsible for Swanpool Garden Suburb, Lincoln; government subsidy houses in Thorpe Bay, Essex; and the layout and design of housing schemes in other parts of the country. After Hennell's death much of James's work was done at Hampstead Garden Suburb, including his own house and several on a larger scale. In partnership with Stephen Rowland Pierce, F.R.I.B.A., James won competitions for three public buildings. Of these the most important was the City Hall, Norwich, on an elevated site between the ancient Guildhall and the Church of St. Peter Mancroft above the market place. A building on a grand scale, it combines James's neo-Georgian architecture with a reference to the then fashionable Swedish movement and the tower of Stockholm City Hall at Ostberg. Norwich City Hall is the most important of the public buildings by James, but the most characteristic is the Hertford County Building. Here he was most in sympathy with the Georgian architecture of the county. He also designed the municipal buildings at Slough, a library for the National Book League, and made additions to All Souls College, Oxford. James, active despite his war injury, was described as a tall man with soft, flexible, and rather boyish features, giving the impression of great sensibility. He had a good deal of quiet humour, affecting a robust attitude to life that contrasted with his appearance. He became A.R.I.B.A. in 1918 and F.R.I.B.A. in 1926, and served as R.I.B.A. vice president 1947-8. He was elected A.R.A. in 1937 and R.A. in 1946, and won the London Architecturebronze medal in 1949. He married the designer Margaret Calkin James in 1922.
