British Whig politician, prime minister and First Lord of the Treasury 1756–57. His appointment was chiefly a convenience to secure the services of William Pitt the Elder as secretary of war, and when by mismanagement he lost the support of Pitt, he was forced to resign.
Career Cavendish's career was a classic example of the importance of patronage and family connections in the way British politics was conducted at this time. He entered the House of Lords in 1754, becoming a privy councillor and Master of the Horse, and being appointed to the key position of Lord Lieutenant to Ireland. In that post he made important friends and appeased hostile factions. He ended his political career as Lord Chamberlain of the royal household 1757–62.
Background The eldest son of the 3rd Duke of Devonshire, he was educated in England. At the age of 21 Cavendish became the member of Parliament for the family seat in Derbyshire. He boosted his political fortunes in 1748 when he married Charlotte, Baroness Clifford of Londesborough, whose father made him a gift of Lismore Castle and large estates in Ireland. He succeeded to the dukedom 1755.
Prime minister At the beginning of the Seven Years' War 1756, Pitt refused to manage the war effort under the premiership of the Duke of Newcastle. As a consequence, Cavendish, with his Whig credentials, parliamentary experience, and friends in Ireland, was recalled to become prime minister November 1756, with Pitt as the power behind the throne acting as war secretary. Cavendish proved as ineffective at managing the process of government in Britain as he had been in Ireland, and soon lost Pitt's confidence. The issue forcing Cavendish's resignation May 1757 was his choice of leader of the House of Commons.
Even by 18th-century standards, Cavendish enjoyed a meteoric career, but his political abilities were limited and he achieved little of significance.