Original: William Cavendish , 4th Duke of Devonshire , KG , PC ( 8 May 1720 2 October 1764 ) , styled Lord Cavendish before 1729 and Marquess of Hartington between 1729 and 1755 , was a British Whig statesman who was briefly titular Prime Minister of Great Britain .
Simplified: William Cavendish , 4th Duke of Devonshire , KG , PC ( 1720 - 2 October 1764 ) was a British Whig statesman who was Prime Minister of Great Britain for a short period of time .