When did John Stuart, 3rd Earl of Bute begin serving as Secretary of State for the Northern Department?
SELECT ?value WHERE { wd:Q294651 p:P39 ?s . ?s ps:P39 wd:Q3954358 . ?s pq:P580 ?value}
john stuart, 3rd earl of bute: Q294651 secretary of state for the northern department: Q3954358