Politician, lawyer and soldier. Born in Petersham (Surrey), he succeeded his brother John Campbell (1680 - 1743), whom he had earlier supported over the 'Act of Union' (1707), earning himself the title of Earl of Islay (1706) in the process. His early career in the army was distinguished, but not as successful as his brother's, who he assisted at the Battle of Sheriffmuir (1715). He turned to the politics and the law, appointed to the Privy Council in 1711. He wielded enormous power in Scottish politics and was not averse to patronage and bribery to ensure his view prevailed. Known as 'the uncrowned King of Scotland', he was the most powerful man in Scotland until the time of Henry Dundas (1742 - 1811), the 1st Viscount Melville. He began work on a seat at Inveraray Castle in 1744, shortly after inheriting the Dukedom and estates from his brother, and although it was completed by 1758, he was never to occupy it. He died in London.