When the 1914-18 War broke out, it was natural that he should serve with the Friends' Ambulance Unit in Italy, of which his cousin Philip Noel-Baker, was first Commandant. After a short post-war period as Assistant Lecturer in his old college, he came to Edinburgh in 1920 as Lecturer under Whittaker.
Bevan Baker was no stranger to Edinburgh as he had married in 1918 Margaret, eldest daughter of the late Dr A H Freeland Barbour. He found Edinburgh a good place to work in. The teaching was interesting and not heavy, the administrative duties were almost non-existent, and research was being actively pursued under Whittaker's guidance. It was in this atmosphere that he did his best work. He gained the Fellowship of this Society in 1921, and the degree of D.Sc. for researches on periodic solutions of dynamical systems in 1923. He played a very full part in the life of the Mathematical Institute, and was for three years Secretary of the Edinburgh Mathematical Society. Bevan was a pianist of almost professional standard and Margaret an excellent violinist, and their many friends will remember with pleasure hearing them play together in their home or at student socials in the University.
In 1924, Bevan Baker was appointed Professor of Mathematics in the Royal Holloway College of London University. Life here was very different; a professor and two lecturers had to do all the teaching for London degrees in both pure and applied mathematics and, although student numbers were small, that proved to be a heavy burden. Research now had to take second place; his time was fully taken up by teaching and by administration, including serving on the Board of Governors of the College and on University Committees. He was a magnificent teacher, and his pupils, some of whom now hold important academic posts, owe much to him and his two colleagues.
He wrote little after he returned to London University. A projected book on Partial Differential Equations of Mathematical Physics was never completed, partly because he was anticipated by Courant-Hilbert and by Bateman. Work on this book did, however, lead to collaboration with the present writer in the monograph "The Mathematical Theory of Huygens' Principle" published in 1939, though his contribution was not as great as he had hoped.
Bevan always overworked, and his health was never robust. Yet, when the Second World War came, he felt it his duty to serve in the Home Guard and, when this proved too onerous, in the A.R.P. But his health broke down in 1944 and he decided to retire at the early age of 54. It was after his retiral that he acquiesced in common usage and adopted the surname Bevan-Baker.
He enjoyed his retiral. It gave him time to recover his health and to enjoy his hobbies - music, gardening and motoring. He and his wife made long continental tours, visiting the Germany he knew as a student and the Italy he learned to love during the First War. But music was his greatest interest. Before he went to the university he wished to take up music as a career, but his family did not approve. After he retired, he worked for the Mus.Bac. degree of London University; but he found, as most of us would, that it is easier to examine than to be examined and he gave up the idea.
After his wife's death in 1961, Bevan-Baker returned to Edinburgh and lived in the University Chaplaincy to Catholic Students. Whilst the old spark and joy of life were still there, he was obviously far from well and he died on July 1, 1963. They had five children, two sons (of whom one died in childhood) and three daughters.