Buchan entered into a career in diplomacy and government after graduating from Oxford, becoming in 1901 the private secretary to Alfred Milner, who was then the High Commissioner for Southern Africa, Governor of Cape Colony, and colonial administrator of Transvaal and the Orange River Colony, putting Buchan in what came to be known as Milner's Kindergarten. He also gained an acquaintance with a country that would feature prominently in his writing, which he resumed upon his return to London, at the same time entering into a partnership in the Thomas Nelson & Son publishing company and becoming editor of The Spectator. Buchan also read for and was called to the bar in the same year, though he did not practise as a lawyer, and on 15 July 1907 married Susan Charlotte Grosvenor—daughter of Norman Grosvenor and a cousin of the Duke of Westminster. Together, Buchan and his wife had four children, Alice, John, William, and Alastair, two of whom would spend most of their lives in Canada. In 1910, Buchan wrote Prester John, the first of his adventure novels, set in South Africa, and the following year he suffered from duodenal ulcers, a condition that later afflicted one of his fictional characters.