Hill preferred the military to the legal profession and secured rapid promotion. He saw service in the Mediterranean, serving on two diplomatic missions, and distinguished himself in Egypt, where he was wounded in 1801. He subsequently served for several years in Ireland. In 1808 he commanded a brigade in Portugal and in the following year joined Wellesley, under whom he served as a commander till the end of the Peninsular War, apart from one period of sick leave, December 1810-May 1811. He was thanked by Parliament for his services at Vimeiro (25 Jan. 1809) and Talavera (1 Feb. 1810). Wellesley recommended him for a knighthood, which he received in January 1812, shortly before displaying great ability in the storming of Almaraz. He was proceeding to winter quarters at Coria when he received the news, in November 1812, of his return for Shrewsbury on the family interest.
He held the seat until his elevation to the peerage without ever being able to attend, though he franked a letter on his arrival at Dover in 1814 before his elevation:
