In 1863 Marlborough joined the British Army, purchasing a commission in the rank of Lieutenant in the Royal Horse Guards. He was initiated into the Freemasonry in January 1871 along with his brother Randolph, in the Churchill Lodge in London. In the following years, he was also initiated into the Ancient Order of Druids. After succeeding to the Dukedom, Marlborough sold the family holdings at Wolvercote and Godstow in 1884.
Personal life
Marlborough was twice married. On 8 November 1869, he was first married to Lady Albertha Frances Anne Hamilton, daughter of James Hamilton, 1st Duke of Abercorn, at Westminster Palace. She was unkindly described by her mother-in-law as "stupid, pious and dull". Before they divorced on 20 November 1883, shortly after Marlborough inherited the dukedom after the death of his father, they were the parents of four children:
While married to Albertha, he fathered an illegitimate son, initially known as Guy Bertrand and later known as Guy Bertrand Spencer, by Edith Peers-Williams who was still married to Heneage Finch, 7th Earl of Aylesford. In an attempt to pressure Lord Aylesford to drop his divorce suit, Lady Aylesford and Marlborough's younger brother, Lord Randolph Churchill, threatened the Princess of Wales that they would subpoena the Prince of Wales as a witness in the divorce.
Guy Bertrand Spencer, whom Marlborough reportedly cared more for than his legitimate children, worked in a brewery. He married, in 1910, Lily Blanche Minnie Saville, who was a coachman's daughter. Spencer served in the Royal Garrison Artillery during World War I. At the end of his life he lived at 2 Glaziers Lane, Normandy, Surrey, England, and died in hospital at Knaphill, Woking, Surrey, on 31 March 1950.
The Duke was cited as one of four co-respondents in the sensational divorce trial of Lady Colin Campbell. He married, as his second wife, Lilian Warren Price, the widow of Louis Carré Hammersley, a New York real-estate millionaire, and a daughter of retired United States NavyCommodoreCicero Price. The civil marriage took place on 29 June 1888 at New York City Hall, with the ceremony officiated by the Mayor of New York City, Abram S. Hewitt. A religious ceremony followed the same day, in the chancel of Tabernacle Baptist Church and presided over by its minister, Dr. Daniel C. Potter. There were no issue from this marriage. The 8th Duke of Marlborough died in 1892, aged 48 at Blenheim Palace, and was succeeded by his only legitimate son, Charles, Marquess of Blandford.