William John Arthur Charles James Cavendish-Bentinck, 6th Duke of Portland, (28 December 1857 – 26 April 1943), known as William Cavendish-Bentinck until 1879, was a British landowner, courtier, and Conservative politician. He notably served as Master of the Horse between 1886 and 1892 and again between 1895 and 1905. Background and education Portland was the son of Lieutenant-General Arthur Cavendish-Bentinck by his first wife Elizabeth Sophia Hawkins-Whitshed, daughter of Sir St Vincent Hawkins-Whitshed, 2nd Baronet and granddaughter of Admiral Sir James Hawkins-Whitshed, 1st Baronet. His paternal grandparents were Lord Charles Bentinck and his second wife Anne Wellesley, the natural daughter of Richard Wellesley, 1st Marquess Wellesley, and a niece of Arthur Wellesley, 1st Duke of Wellington. Lord Charles was the third son of Prime Minister William Cavendish-Bentinck, 3rd Duke of Portland by his wife Lady Dorothy Cavendish, daughter of William Cavendish, 4th Duke of Devonshire. Portland's mother died only a few days after his birth. He was educated at Eton. He inherited the Cavendish-Bentinck estates, based around Welbeck Abbey in Nottinghamshire, from his cousin William Cavendish-Scott-Bentinck, 5th Duke of Portland, in 1879. He also succeeded his stepmother as second Baron Bolsover in 1893. His half-sister Lady Ottoline Morrell was a society hostess and patron of the arts associated with the Bloomsbury Group. Public life Portland initially embarked on a military career and served as a lieutenant in the Coldstream Guards from 1877 to 1880, and then as lieutenant-colonel of the part-time Honourable Artillery Company from 1881 to 1889. He was honorary colonel of the 1st Lanarkshire Artillery Volunteers from 1884 to 1891, and of the 4th (Militia) Battalion of The Sherwood Foresters from 1889, and of the latter regiment's 7th (Robin Hood) Battalion (Volunteers, later Territorial Force) from 1898. He sat on the Conservative benches in the House of Lords and held office as Master of the Horse under Lord Salisbury from 1886 to 1892 and from 1895 to 1902 and under Arthur Balfour from 1902 to 1905. In 1886, he was sworn of the Privy Council. He was made a Knight Grand Cross of the Royal Victorian Order (GCVO) in 1896, and was a holder of the Royal Victorian Chain. In 1900 he was appointed a Knight of the Garter, receiving the insignia in an investiture by Queen Victoria at Windsor Castle on 16 March 1900. He was appointed a Knight of Justice of the Order of the Hospital