He succeeded his father, Gilbert George Reginald Sackville, as 9th Earl De La Warr at the age of 15. After Eton he served in the First World War in the Royal Navy as an Able Seaman. This experience, followed by that gained at Oxford after the war, probably accounts for his early acceptance of Socialism. The 9th Earl De La Warr was the first hereditary peer to sit on the Labour Benches. He held the following positions and offices: Parliamentary Under-Secretary War Office 1929-1930; Parliamentary Secretary Board of Education 1935-1936; Parliamentary Under-Secretary of State for the Colonies 1936-1937; Lord Privy Seal 1937-1938; President of the Board of Education 1938-1940; Chairman Estate Committee National Trust 1950-1951 and 1955-1970; Postmaster-General 1951-1955; Chairman Agricultural Research Council 1944-1949; Lord-in-Waiting 1924 and 1929-1931; Chairman Joint East and Central Africa Board 1955-1958; Chairman Royal Commonwealth Society 1960. He joined the Conservative Party later in life.
As Mayor of Bexhill from 1932-1935 he instigated the competition for the design of the De La Warr Pavilion as seen today. In 1920 he married Diana, daughter of Gerard Leigh and Mrs Halsey. They had two sons and one daughter. The elder son, William Herbrand, succeeded as 10th Earl De La Warr in 1976. The younger son, Flying Officer Thomas Henry Jordan Sackville, born on the 13 November 1922, was killed whilst on operations on the 14 May 1943 aged 20 years. His first wife died in 1966 and in 1968 he married Sylvia, Countess of Kilmuir. He died on the 28 January 1976.