Challenging the conventional interpretation of Mary of Guise as the defender of Catholicism whose regime climaxed with the Reformation Rebellion, Pamela Ritchie shows that Mary was, on the contrary, a shrewd and effective politique, whose own dynastic interests and those of her daughter took precedence over her personal and religious convictions. Dynasticism, not Catholicism, was the prime motive force behind her policy.Mary of Guise’s dynasticism, and political career as a whole, were inextricably associated with those of Mary Queen of Scots, whose Scottish sovereignty, Catholic claim to the English throne and betrothal to the Dauphin of France carried with them notions of Franco-British Imperialism. Mary of Guise''s policy in Scotland was dictated by European dynastic politics and, specifically, by the Franco-Scottish alliance of 1548–1560. Significantly more than a betrothal contract, the Treaty of Haddington established a ‘protectoral’ relationship between the ‘auld allies’ whereby Henri II was able to assume control over Scottish military affairs, diplomacy and foreign policy as the ‘protector’ of Scotland. Mary of Guise’s assumption of the regency in 1554 completed the process of establishing French power in Scotland, which was later consolidated, albeit briefly, by the marriage of Mary Stewart to Francois Valois in 1558. International considerations undermined her policies and weakened her administration, but only with her death did Mary of Guise’s regime and French power in Scotland truly collapse.