In 1780 Henniker unsuccessfully contested his father’s first constituency of Sudbury, but is not known to have stood anywhere in 1784. In 1785 he was returned at New Romney on the interest of Sir Edward Dering, and in the House he was an independent supporter of Pitt. In one of the divisions on Richmond’s fortifications plan he voted against Government: his name does not appear on either side in the only extant list, that of 27 Feb. 1786, but speaking on the army estimates, 10 Dec. 1787, he ‘boasted to have been one of those who gave a vote against the system of fortifications, which had been proposed ...’ In doing so he claimed to have done ‘essential service’ to Pitt, ‘and stood forward, with many other of his friends, to shield him from the consequence of a measure, that ... must have brought mischief on himself and the country’. He now supported the Government proposals, and spoke of Pitt as a minister who ‘had brought the country to an elevation of glory from a depressure of despondency’.
He left a few antiquarian studies, among them an ‘Account of the Families of Henniker and Major’. He died 4 Dec. 1821.
