== Post-regency ==

[[File:YoungMaryStuart.jpg|thumb|upright|left|Mary, Queen of Scots, by [[François Clouet]], {{Circa}} 1555]]

 

In the first months of the [[Scottish Reformation]] Châtellerault continued to support Mary of Guise. He faced a Protestant army with the French commander at [[Cupar Muir]] in June 1559. He changed his allegiance in August 1559, joining the Protestant [[Lords of the Congregation]] to oppose the regency of Mary of Guise, and lost his French dukedom as a result. In order to discredit him with the English government a letter was forged by his enemies, in which Châtellerault declared his allegiance to Francis II of France, but the plot was exposed. On 27 February 1560 he agreed to the [[Treaty of Berwick (1560)|Treaty of Berwick]] with Queen [[Elizabeth I]] of England, which placed Scotland under English protection.{{Sfn|Chisholm|1911a|p=[[:s:1911 Encyclopædia Britannica/Arran, Earls of|643, third para, line twenty]]|ps=: "On the 27th of February 1560 he agreed to the treaty of Berwick with Elizabeth, which placed Scotland under her protection."}}