William Henry Sewell was born around 1786, the son of Robert and Sarah Sewell, grandson of Sir Thomas Sewell and brother of Major General Robert Sewell. He was educated at Westminster and Eton, and joined the army as an ensign in the 60th Foot on 27 March 1806 but later exchanged to the 16th Light dragoons. He was ADC to Lord Beresford and joined the army in Portugal in 1808. He was at one time on the staff of the Portuguese army and commanded a Portuguese cavalry regiment. He endured the retreat to Corunna. He then served in the Peninsula at Talavera, Busaco, Ciudad Rodrigo, Badajoz, St Sebastian, Nivelle, Nive, Bayonne, Orthes and Toulouse. He then served in India for the next 28 years.
In India he was promoted to major-general on 9 Nov 1846, and appointed Deputy Master-General of the Ordnance, then put in command at Bangalore. He was Commander-in-Chief of the Madras Army and returned to Britain in 1854 where he was appointed Colonel of the 79th Cameron Highlanders on 24 Mar 1854. He retired in 1856 and appointed KCB in 1861. He died in Florence on 13 March 1862 and buried in the Protestant Cemetery: Cimitero Acattolico, Florence.
He was married in 1831 to Georgiana Hacking Hamilton-Dalrymple, daughter of Sir John Hamilton-Dalrymple 5th Bt. They were married in St George’s Cathedral, Madras and had seven children;
William Robert Dalrymple Sewell 1833 - 59
John Dalrymple William Sewell 1836 - c1905
Henry Fane Haylett Sewell 1838 - 1910
Charlotte Fanny Jane Sewell 1840 - 1841
Julia Helen Sewell 1844 - 1895
Charlotte Jane Lindsay Cavendish Sewell 1845
Caroline Georgiana Sewell 1850 - 1893
