After leaving school, he attended the Royal Military College, Sandhurst and, passing out with honours, he joined the Queen's Own Cameron Highlanders in 1903.

[1] Robertson played rugby for Fettesian-Lorettonian, London Scottish, Monkstown, Edinburgh Wanderers, and United Services Portsmouth.

In the last year, he was captain of the Army XV but he voluntarily offered to relinquish his position because he deemed himself out of form and unworthy of it, according to an article published after his death in Windsor Magazine.

The following year, 1912, he played in every game for Scotland (except the France match), including the one against the South African side on tour of the Home Nations.

[7] Robertson passed out of RMC Sandhurst with honours, and joined the 1st Battalion Queen's Own Cameron Highlanders as Second Lieutenant on 22 April 1903.

[19] At the outbreak of the First World War, Robertson was recalled to the depot in Inverness, and was then briefly at Aldershot before his regiment crossed to France in September 1914 to fight on the Aisne.