Buchan was the son of a Free Church minister, and grew up in Fife, spending many holidays at his grandparents' house in the Scottish borders. He read classics at Glasgow University, winning a scholarship that enabled him to continue his studies at Oxford. After graduating, he went to South Africa in the aftermath of the Boer War as aide to Alfred Milner. He enjoyed this work, and had hopes of a career in the colonial service, but it came to nothing. After an unsuccessful attempt to make his way as a lawyer, he went into publishing. In 1907, he linked himself to the English aristocracy by marrying the Duke of Westminster's cousin, Susan Grosvenor. In the years immediately before World War I, he started to make a name for himself as a writer of adventure stories. The most celebrated, The Thirty-nine steps, appeared in 1915. During World War I he continued to write adventure stories in between propaganda work for the government and reporting the war for the Times. Amongst other things, he produced a multi-volume popular history of the war, more-or-less in real time. After the war, Buchan settled down in a country house outside Oxford, churning out quantities of biographies and historical novels as well as the popular adventure stories featuring Richard Hannay, Sir Edward Leithen, and Dickson McCann. He also became a Unionist MP, holding minor ministerial appointments. He also held minor ceremonial appointments, twice serving as lord high commissioner to the General Assembly of the Church of Scotland. In 1935 he was appointed Governor-General of Canada. At the time, this was an appointment that went with a peerage, so he became Baron Tweedsmuir. He died, whilst still in office, in 1940.