Cavendish, Lord Frederick Charles (1836–82), chief secretary for Ireland, was born 30 November 1836 at Compton Place, Eastbourne, second son of William, 7th duke of Devonshire, and his wife, Blanche Georgiana (née Howard), daughter of the 6th earl of Carlisle. He had a sister and two brothers (the elder of whom, as marquis of Hartington (qv), was chief secretary for Ireland 1870–74). Educated at home and at Trinity College, Cambridge (BA 1858), he was private secretary to Lord Granville 1859–64 and then liberal MP for north-west Yorkshire from 1865 until his death.
In July 1872 Cavendish became private secretary to the prime minister, Gladstone – to whom he was particularly close, having married (1864) Mrs Gladstone's favourite niece, Lucy Caroline Lyttelton (1841–1925). He served as a lord of the treasury from August 1873 until Gladstone's government resigned in February 1874. When the liberals returned to power in 1880, he was appointed financial secretary to the treasury. As Gladstone was combining the office of chancellor of the exchequer with that of prime minister, it fell to Cavendish as financial secretary to do the routine work of the chancellor.
When W. E. Forster (qv) quit as chief secretary for Ireland in May 1882 in protest at the so-called ‘Kilmainham treaty’, Cavendish succeeded him (but, unlike Forster, outside the cabinet; Earl Spencer (qv), as lord lieutenant of Ireland, had the cabinet seat). Gladstone intended that the ‘treaty’ should inaugurate a policy of conciliation in Ireland, and his reason for appointing Cavendish was that the latter had, while at the treasury, drawn up a new land purchase scheme for Ireland. However, on his first day in Dublin (6 May 1882), Cavendish was assassinated near the viceregal lodge in the Phoenix Park by men wielding long surgical knives. He was walking with the under-secretary, Thomas Henry Burke (qv), who was also killed. The assassins belonged to an extremist Fenian society known as the Invincibles; five were later hanged (see under Joe Brady (qv) and James Carey (qv)). It was believed that Burke, not Cavendish, was their target.
Cavendish had a speech impediment, and that seriously compromised his effectiveness as a politician. But for his Cavendish name and Gladstone connection, it is unlikely that he would ever have held office. His appointment as chief secretary was greeted with incredulity, even derision. Nevertheless, he was regarded as amiable, high-minded, and industrious. His funeral was huge, reputedly attended by 30,000 people, including 300 MPs. He is buried in his family's plot in Edensor churchyard, near Chatsworth, Derbyshire, principal seat of the dukes of Devonshire. By a strange irony, next to his grave is the grave of Kathleen, sister of John Fitzgerald Kennedy, first US president of Irish catholic descent, who married (1944) William, marquis of Hartington, grandson of Cavendish's nephew, the 9th duke; a tablet records that President Kennedy visited her grave 29 June 1963, less than five months before his own assassination.
Cavendish's wife was second daughter and second of twelve children of the 4th Lord Lyttelton and his first wife, Mary (née Glynne), a sister of Mrs Gladstone. Their marriage was childless, and her widowhood lasted forty-three years. She showed remarkable forbearance and generosity in her misfortune. Thus, she wrote to Earl Spencer immediately after her husband's death that she ‘could give up even him if his death were to work good to his fellow-men’ (quoted in The diary of Lady Frederick Cavendish (1927)). Moreover, she sent a little crucifix – as a sign of forgiveness – to the first of the men executed for the murders of Cavendish and Burke; T. M. Healy (qv) became aware of this very private gesture, which is confirmed by her nephew, George Lyttelton, albeit in a garbled version. She later supported home rule, and was identified with a number of other causes, notably in the field of education. Lucy Cavendish College, Cambridge, is named after her. Portraits by Sir William Richmond of Cavendish and his wife hang in Holker Hall, a Cavendish house at Cark-in-Cartmel, Cumbria.