South Africa Walker was employed as a lecturer at the
University of Bristol for a short time, where he co-wrote a textbook for secondary schools on English history that remained in publication for a long time. In 1930, Walker gave an influential lecture in Oxford, printed as
The frontier tradition in South African history (Oxford University Press, London, 1930), in which he outlined his theory that the origins of the
apartheid system in South Africa lay in conflict between blacks and whites on the frontier regions in the nineteenth century which was then imported into the interior where it was institutionalised in the constitutions of the
Orange Free State and the
South African Republic. Walker's theory owed much to
Frederick Jackson Turner and
The Oxford History of Historical Writing described him as "in some respects the
George Stanley of South Africa". He continued to write, but with a wider focus than previously now that his chair enjoyed the title of "Imperial". He acted as an
air-raid warden in Cambridge in
World War II. By 1942, he was the only history professor still teaching at the university; most of the students and teaching staff had left for the war.
Retirement Walker retired in 1951, but continued to write. He produced a third edition of his history of South Africa in 1957 (retitled
A History of Southern Africa) and edited the second edition of the South African volume of
The Cambridge History of the British Empire, published in 1963. This last, however, was criticised for not following the latest historical methods. In 1968, Walker, and wife Lucy, returned to South Africa, where he died in Durban in 1976. ==Personal life==