When John Buchan sailed for Canada in October 1935 to be sworn in as Governor-General, he knew that it was a unique opportunity to help the senior Dominion become a fully sovereign state, and to help strengthen relations between the British Empire and the United States. This chapter examines how Buchan, as Lord Tweedsmuir, carried out his role as Governor-General in a new form of the role, created by the 1926 Imperial Conference, which resulted in Governors-General no longer representing the British government but representing the Sovereign of an autonomous state. This agreement was confirmed in the 1931 Statute of Westminster. It marked an important step in constitutional evolution, a legal and political aspect of modernity that reflected, after an age of empires, the growing desire for local autonomy. This desire was enabled by a growing acceptance, following their roles in World War One particularly, to let the Dominions assume responsibility for their foreign and domestic policies. The spirit of the times was embodied in the appointment of Tweedsmuir, a commoner ennobled to honour the office, but also a man of the people, to be the King's representative in Canada. Tweedsmuir understood both the evolution, and strength, of national sentiments, and how this new context meant that Britain and the Dominions were now legal equals on the international stage. His challenge was to transform the office of Governor-General into a modern institution, reflecting the authority now devolved to this country.