Jenkinson’s great-grandmother was a Bankes, relations between the two families were close, and in March 1764 John and Henry Bankes considered the possibility of returning Jenkinson for Corfe Castle, which they did in 1768 and 1774 without contest.
Jenkinson owed his original appointment at court probably to Lord Harcourt, a friend of his family; his career in the army, Parliament, and in office mainly to his brother Charles. It was to him that he was indebted for his promotion in 1762,
John Jenkinson was offered the Irish post by Harcourt within a month of Harcourt’s being offered the lord lieutenancy.
In Parliament Jenkinson always voted with the Government. During his twelve years in the House only two speeches are reported: 31 Jan. 1772, on a motion of Thomas Townshend jun. about the export of horses; and an intervention in the debate of 6 Feb. 1772 on the 39 Articles.
