After the outbreak of the Boer War in South Africa in 1899, Giles was sent there as war correspondent and artist by "The Graphic" and the "Daily Graphic", and was attached to French's 1st Cavalry Brigade. He witnessed the surrender of General Piet Cronjé after the Battle of Paardeberg, and was present at the subsequent relief of Kimberley. Later he wrote a piece for The Graphic titled "With French to Kimberley and Roberts to Bloemfontein" which appeared in "The Graphic History of the South African War". Giles contributed greatly to the pictorial record of the Boer War with works on display in museums in both South Africa and England. He was awarded the Queen's South Africa Medal on 12 February 1903.