The Third Duke of Portland served twice as Prime Minster and had a long and distinguished political career from 1760s to the 1780s. This study details how he was transformed from a pillar of the grand Whiggery (he was the brother-in-law of Georgiana, Duchess of Devonshire) into the figurehead for would-be Tories. The book also examines how he played an important public role in many of the political crises of his era (including the French Revolution and the Union) as well as a hidden role in British history (he was involved in the secret service and political corruption).