Cavendish, William (1698?–1755), 3rd duke of Devonshire , lord lieutenant of Ireland, was the eldest son of William, 2nd duke of Devonshire, and his wife, Rachel Russell, daughter of William, Lord Russell, and sister of the 2nd duke of Bedford. Heir to one of the great whig dynasties – his grandfather, the 1st duke, was one of the first supporters of King William (qv) – he grew up, with two brothers and a sister, at the family seat at Chatsworth in Derbyshire, and from 1707 enjoyed the courtesy title of marquess of Hartington. He was educated at New College, Oxford, and in 1721 became a member of the English house of commons, where he sat until he succeeded his father in 1729. He was married in 1718 to Catherine Hoskins, only daughter and heir of John Hoskins, of Oxted, Surrey, and his wife, Catherine. His father-in-law, a landowner and rich merchant, was steward to the duke of Bedford; the younger Catherine brought her husband money, and bore him four sons and four daughters.
Devonshire's appointment to high office arose from his name and social position rather than from any special ability, and he inclined more to pleasure than to business; his drinking, even in a tolerant age, was considered notable. His unpretentious manner, sociability, and equable temperament, however, combined with an appreciation of political and social connections and a sure hand in dispensing patronage, were not negligible characteristics, especially in Irish politics. Like his father, he was a friend of Sir Robert Walpole, the dominant figure of English politics. He was appointed lord steward of the household (a post previously held by his father and grandfather) in 1723, and was lord privy seal 1731–3.
He was appointed lord lieutenant of Ireland in 1737 and remained in the post until 1745, making his the longest continuous tenure of the office in the eighteenth century. His viceroyalty was not especially eventful; his first session of parliament, disturbed by a controversy over coinage, was probably his most difficult. The enormous distress caused by the extreme severity of the winter of 1739–40 and the consequent crop failures and famine (the worst of the century) prompted private charitable initiatives, but, naturally for this period, was not thought to require intervention by the government. He encouraged the composer George Frederick Handel (qv) to undertake concerts in Dublin; these were crowned by the first performance there of ‘Messiah’ on 13 April 1742.
He applied himself to careful management of the competing factions among the Church of Ireland elite, who dominated the Irish house of commons, and whose votes were required to pass the supply bills. A notable development was the consolidation of the Ponsonby family's political power, promoted by the marriage of William (qv) and John (qv), elder sons of Brabazon Ponsonby (qv), Lord Duncannon, to two of the duke's daughters, in 1739 and 1743, and the elevation of Duncannon himself to the earldom of Bessborough. William Ponsonby also served as chief secretary during the latter years of the duke's viceroyalty, in succession to Sir Robert Walpole's son Edward.
The Irish connections of Devonshire's family were also strengthened by the marriage of his eldest son, William Cavendish (qv), to Lady Charlotte Boyle, heir to the earl of Burlington's extensive estates in Ireland. Though a brilliant dynastic match (and a harmonious one) the groom's mother resolutely opposed it, for reasons which, apart from the couple's disparity in age, are obscure. However, a grave rift developed between the duchess and the rest of her family; this became publicly known and precipitated the duke's withdrawal from the court and from public life in 1749. He died 5 December 1755, and was succeeded as 4th duke by William, who by this time himself held the office of lord lieutenant of Ireland. The Irish connections did not end with his son: his grandson, the 5th duke, was in 1773 one of five peers resident in England but with large estates in Ireland who protested at a proposed absentee tax.