William Cavendish, Marquess Of Hartington

William John Robert Cavendish, Marquess of Hartington, was born on 10 December 1917 in London, England. He was the eldest son of Edward Cavendish, the 10th Duke of Devonshire, and Lady Mary Gascoyne-Cecil. As the heir apparent to the dukedom, he held the courtesy title of Marquess of Hartington.

His education included attendance at Eton College and Trinity College, Cambridge. Cavendish was affiliated with the Conservative Party and was selected as the official candidate of the Wartime Coalition for the West Derbyshire constituency in the by-election held on 18 February 1944. The constituency was geographically close to Chatsworth House, the family estate. During the campaign, he opposed Charles Frederick White Jr., who resigned from the Labour Party to run as an Independent candidate, thereby circumventing the wartime coalition's restrictions on partisan campaigning. Despite the campaign efforts, Cavendish was defeated, garnering 41.5% of the vote against White's 57.7%. West Derbyshire had experienced continuous Conservative representation since 1923, initially held by Cavendish's father and subsequently by his uncle by marriage.

During World War II, Cavendish served as an officer in the British Army's Coldstream Guards. His military service involved participation in the Western European campaign during the liberation of Nazi-occupied territories. In August 1944, as part of the Guards Armoured Division's 5th Battalion Coldstream Guards, he saw heavy combat in France. The battalion crossed the River Somme and advanced eastward towards Brussels, which it helped liberate. He documented his experiences, expressing feelings of unworthiness and longing for his wife amid the chaos and national celebration.

On 9 September 1944, Cavendish was killed in action at the age of 26. He was shot by a sniper while leading a company during an operation to capture the town of Heppen in Belgium from German Waffen-SS troops. He is buried at the Leopoldsburg War Cemetery.

In his personal life, Cavendish married Kathleen Kennedy, the American socialite and daughter of Joseph P. Kennedy Sr., on 6 May 1944. The marriage took place at the Register Office in Chelsea Town Hall, London. Kathleen Kennedy was the sister of John F. Kennedy, Robert F. Kennedy, and Ted Kennedy. The marriage was attended by her father, Joseph P. Kennedy Sr., and her brother Joseph P. Kennedy Jr., who was then serving as a lieutenant in the U.S. Navy. The Duke of Devonshire and Kathleen Kennedy’s mother, Rose Kennedy, reportedly disapproved of the marriage due to religious differences; the Kennedys were Catholic, while the Devonshires were Anglican.

William Cavendish’s death occurred shortly after his marriage, less than five months later. He was interred at the Leopoldsburg War Cemetery.