 Walker was born in Streatham, London on 6 September 1886 to William Walker, a mercantile clerk of Scottish descent, who worked for Union-Castle Line and Jessie "née" Goodman.He began his education at Mill Hill School, followed by a scholarship to Merton College, Oxford, from where he graduated in modern history with a first class (1908).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.