In 1763, and again in 1768, Warkworth was returned unopposed for Westminster. In Parliament he, like his father, supported Grenville’s Administration, and on 26 Feb. 1764 Grenville himself referred to Warkworth’s ‘constant and kind attendance’ during the debates on general warrants.
In April 1774 Percy’s regiment was ordered to America, and though his parents strongly opposed his going there, and his mother applied to the King to have him exempted, Percy insisted that ‘it was his indispensable duty to accompany his regiment’.
A change of Administration or measures would be, at this instant, the most fatal thing in the world to this province, and all America in general, for it would be adding fresh fuel to that flame which the frequent changes in both were the origin of.
Nevertheless, Robinson’s survey of September 1774 classed Percy as an opponent, and during the election contest in which Percy was re-elected at the head of the poll, a pamphlet addressed to the electors of Westminster, defending his absence on active service in America, stated: ‘It is well known his Lordship disapproved of those very measures which rendered the present service necessary.’
He died 10 July 1817.
