Robert Bertie, 4th Duke of Ancaster and Kesteven

About 1777, he served as a volunteer in North America. A lieutenant in the 7th Regiment of Foot, on 20 January 1778, he was promoted to a captaincy in the 15th Regiment of Foot.^[2]

On his father's death on 12 August 1778, he succeeded as 4th Duke of Ancaster and Kesteven, 4th Marquess of Lindsey, 7th Earl of Lindsey, 20th Baron Willoughby de Eresby and Hereditary Lord Great Chamberlain. He was the last to hold the Lord Great Chamberlainship as an undivided office. On 12 February 1779 he was invested as Privy Counsellor and was Lord Lieutenant of Lincolnshire.

He never married and died in Grimsthorpe on 8 July 1779 from scarlet fever. At the time of his death he was engaged to Lady Anna Waldegrave, daughter of James Waldegrave, 2nd Earl Waldegrave, and Maria Walpole, the illegitimate granddaughter of Sir Robert Walpole, the Prime Minister. After his death, his fiancée married Lord Hugh Seymour. He was buried on 22 July 1779 in Edenham.

On his death, the Hereditary Lord Great Chamberlainship and the Barony Willoughby de Eresby fell into abeyance between his two sisters, all other titles of his passed to his uncle. An illegitimate daughter of the 4th duke, Susan, was married to Banastre Tarleton; but there were no children.