Fuller was born in Chichester, West Sussex and is the son of an Anglican clergyman. After moving to Lausanne with his parents as a boy, he returned to England at the age of 11 without them; three years later, at "the somewhat advanced age of 14", he began attending Malvern College and, later trained for an army career at the Royal Military College, Sandhurst, from 1897 to 1898. His nickname of "Boney", which he was to retain, is said to have come either from an admiration for Napoleon Bonaparte, or from an imperious manner combined with military brilliance which resembled Napoleon's.