He later served as president, and then as chair, of the National League of Young Liberals, and completed a doctorate at the University of Edinburgh.
In 1953 he was a Liberal candidate for East ward in the Bethnal Green Metropolitan Borough Council elections.
[2][3] He stood for the Liberal Party at numerous Parliamentary elections: in Merton and Morden in 1950, Bethnal Green in 1951 and 1955, and Gainsborough in 1959 and 1964.
[2][3] In the run-up to the 1975 United Kingdom European Communities membership referendum, Douglas chaired the Liberal "No to the Common Market" Campaign.
He wrote numerous books, including Surrey: The Rise of a Modern University and The History of the Liberal Party 1895-1970.